Big Bang has Big Brown Patches!

[d3spot]

These plants have been vegging for about 4 weeks now under a 600w HPS. They are about 7 weeks old from seed. Two of them had a problem with brown spots when they were young which I posted about here -> link. This problem didn't get much worse than that and didn't spread much at the time. Now as you can see from the pictures above a similar problem is afflicting one of the four pretty bad. All four of the leaves on the same level as the one pictured are in a similar state but this is the worst. Also the other plants have started developing some similar spots.

Has any one got any ideas as to a cause or remedy?

I am using a 600w HPS light and in a 6ft x 4ft x 7ft room with a large inline fan and an oscillating fan blowing over the tops of the plants. The temperature ranges from 64F - 83F and the humidity ranges from 30 - 60 %. They are planted in 15ltr pots in a 65/35 mixture of standard garden center own brand multipurpose compost and perlite. I have been giving them 5/6ths of a pint of water each roughly every 2-3 days. I have been mixing Plagron Terra grow into the water at a 1:200 ratio every time I water. The PH of the soil is about 7 and is highest in the offending plant's pot.

Could the high PH be the cause of the problem? I've got some hydro PH down and was going to mix this into the water. Is it OK to use this for soil?

I have also noticed this on another plant. You can't really see in the picture but the leaf is looking quite yellow toward the left side. Any Ideas?

 

[mountainNick]

Are you using any foliar feeding or sprays? If you have then you are using too much or too often. Could be too much ferlilizer, maybe give the nutes every second watering.
If the problem has been there from the start, it could be the compost. Do u know its NPK?
Peace

 

[EvilTwin]

d3spot,
That mixture you were using while they were young was a seed and cutting mix. Very mild and then you were using deionized water. So your plants got off to a bad start.

You aren't still using the de-ionized water are you? If not, what water are you using?


It really looks to me like you need to up the nutes. Make sure your water has some Ca in it and see if that helps.
ET

 

[d3spot]

I'm not using any sprays. The last time they got watered this plant got pure water. I was going to start flowering next week so i'm going to give them all pure water for a week before I switch to the bloom nutes. Do you think this would clear up the problem? Should i give switch to feeding every other watering with the bloom nutes?

I'm not sure about the NPK of the soil it is b&q's (a british hardware chain) standard multipurpose stuff so i guess the nute content is pretty low. They were initally potted in diferent soil (this stuff -> link) but they have been in the new stuff for about 4 weeks now.

 

[d3spot]

Hey EvilTwin.

I am still using the de-ionised water mixed with the plagron. Is that bad? I thought it was better than the tapwater it is verry hard where I live. What should I be using?

I thought Ca was bad. I'm sure it is inmy tap water but too much I think. Sould I mix the tap water with the de-ionised stuff?

What about the PH down? It is phosphoric acid.

 

[EvilTwin]

In answer to your question...yes you can use hydro ph down on soil. How did you measure the soil ph?

And are you using tap water? Do you know if it's hard water (lots of disolved solids in it)?
ET

 

[EvilTwin]

Hey EvilTwin.

I am still using the de-ionised water mixed with the plagron. Is that bad? I thought it was better than the tapwater it is verry hard where I live. What should I be using?

I thought Ca was bad. I'm sure it is inmy tap water but too much I think. Sould I mix the tap water with the de-ionised stuff?

What about the PH down? It is phosphoric acid.

ooops, we were posting at the same time.

Too much Ca is bad, but also too little Ca is also bad. Brown spots on leaves is often related to a Ca deficiency. Ca is an important plant nutrient.

De-ionized water has a different meaning over here in the states. Is it distilled water? If you're going to the store and buying it in gallons...next time look for RO water. (reverse osmosis)

Anyway, since you probably don't have an EC meter, try mixing your tap water with the stuff you were using. Far as ratio...when you say the water is very hard...maybe 1/3 tap water then to start. And the addition of the tap water will also raise the ph so drop it down with the phosphoric acid. To low 6 ph...
ET

 

[redbull834]

In answer to your question...yes you can use hydro ph down on soil. How did you measure the soil ph?

And are you using tap water? Do you know if it's hard water (lots of disolved solids in it)?
ET

Hi bro

Have a look at this RO unit in the UK

http://www.h2onics.co.uk/shopping/product.php?productid=15

 

[d3spot]

Hey ET. Yeah I think we had our inter-tubes crossed for a while back then.

Thanks for the info on Ca. I didn't know I need it. I will try adding some tap water next time. The water i'm using is sold for car batteries I think here is a link to the wiki page -> link.

I have to sleep now, it's late here and I have work in the morning. Thanks for your advise. I'll check back tomorrow evening.

 

[d3spot]

Hey redbull.

Thanks for the link to the RO filter, damn those things are expensive. Not sure if I can afford one just yet. The de-ionised water only cost 60p per liter. do you thinkit is ok to stick with that instead?

Deionization does not remove the hydroxide or hydronium ions from water. These are the products of the self-ionization of water to equilibrium and therefore are impossible to remove.

Do you think this would effect the plants?

 

[EvilTwin]

Hey ET. Yeah I think we had our inter-tubes crossed for a while back then.

Thanks for the info on Ca. I didn't know I need it. I will try adding some tap water next time. The water i'm using is sold for car batteries I think here is a link to the wiki page -> link.

My reasoning is that the store bought nutrients are probably devoid of Ca as well as the water you're using. So the plant only has the Ca in the soil.

I don't know anyone who grows with de-ionized water. It's recommended for storing ph pens is all I know about it.
ET

 

[mountainNick]

Ya give bloom every second watering and if you flush good at the end you will have some clean tasting buds
Peace

 

[BigForest]

Hate to put folks under the bus greenhouse that is but i have been mis diagnosing this same problem for 2 months lil brown and or rust type spots in vegg turning the tips black and then futher necrsois i have relentlessly been pulling all bad leaves to maintain some control now i have several+ strains in my vegg garden so i can see whose more immune to this fungus or what ever.I've been looking on here the mag that is and i've heard everything from ca def. to k def. high hum, tapwater,I've went thru it all alg-mic,cal-mag,magic cal,omri fungi-cide spray and powered.Ive covered all these fix it's. air movement air exchange.And i've narrowed it down to a couple strains and there all green house i have a chesse that was riddled by this fungi as what im calling it now.From greenhouse when i watched the htcc dvd from last year arjan is speaking about gardening at the end. And he says theres a new disease or something spreading and to pull the leaves as soon as you see.Well i have a greatwhite shark in badshape,a white rhino holding it off,and i won a mix pack and began to pop this girls.
Is when my problems started to exist spreading thru all the garden the mature girls immune system didnt realy let it do much now once ive quarintine these strains my mmfungus or what ever it is problems seem to decline.nothing work except when i quarintine some specific plants and it will spead u must contain it quickly.

 

[jyme]

i would keep an eye on the ph of your run off and if your water is ph7 thats not bad the leafs are telling me that your girls are in desprate need of (CA) this is immoble and you should give them folar feedings with garden lime