Fan leaves clawing w/ dead patches

[pickledLSD]

The plant is almost 5 weeks into flowering now. I feed 3 tsp of PBP bloom, 1 tsp of CalMag, and 1 tsp of Sweet at every watering (once every 4-5 days). Runoff ph is alway 6.0-6.2 and temps range from lower 70s to upper 80s. She's in a mixture of FFOF and Miracle Grow organic soil under a 250w HPS. Everything looks good except the fan leaves.

Two waterings ago I stopped using the CalMag and used only 2 tsp of PBP bloom because I thought she was showing a little nute burn. Then these problems started. Lastnight I switched back to my original mixture.

 

[TNJed]

It's fairly normal for the plant to feed on the larger fan leaves during the last few weeks of flowering, due to low levels of N in bloom ferts. You may want to alternate your Swwet and Cal/Mag because they both contain a good bit of Mag. Other than that, things seem like they are going fine by the look of your pics. Good luck!!

 

[MTF-Sandman]

Has the environment changed any recently? Temps, RH or airflow are fairly common causes of the leaf edges doing that...but nute burn can do it as well.

 

[pickledLSD]

No recent changes inside the box.

Here's what I'm thinking, tell me if it sounds stupid. At first it was just doing the clawing and slightly burnt tips. I slacked off on the Bloom and CalMag. Then the dead patches started showing up and could be a deficiency. So maybe I went from overfeeding to underfeeding. TNJed said Sweet and CalMag both have a decent amount of Mag. I'm going to try using 3tsp of bloom and 1 tsp of Sweet with every watering. Every third watering I'll swap the 1tsp of Sweet with 1 tsp of CalMag. Opinions?

 

[MTF-Sandman]

I think I'd flush them first...I finish plants at 15ml PBP & 4-5ml CM and some of them even burn a little.

What's the PPM's been doing as this has been going on?

 

[pickledLSD]

No idea on the ppms. I've been telling myself I'm getting a meter for some time now.

 

[Blackmelo]

hi pickled, you do not need a meter for the ppm. You can actually work out how much your mix will theoretically contain and save yourself alot of money.
If you are interested, have a read through this article:
http://www.angelfire.com/cantina/fourtwenty/articles/profiles.htm

Not only did this article tell me the exact nutrient needs of cannabis(ie green plants all the way), it also gave me the opportunity to work out the ppms I was feeding and thus judge how my original mix was wrong. I ended up buying some slight nute additives to make my mix perfect. I've been using my new mix according to the info on that site for 3 grows already and have never looked back.

Now if you have a look at that site, I am suspecting you will find out that you were indeed feeding a bit too much. A fellow grower I taught to grow last year completely ruined his crop by feeding one tablespoon of epsom salts where I had said feed a teaspoon...

You are feeding 15ml of PBP and by the sounds of things too much cal/mag. Listen to MTF when he says that amount can burn plants.

PS: you mentioned 15ml every watering but you haven't actually mentioned how much that is mixed in to.

Like I said, I reckon you are overfeeding slighly but your plants actually looks really good.

 

[Blackvelvet]

Continue the original feeding mix of 15 ml pbp bloom (for soil, right?) + the 5 ml cal mag plus. But, stop using the sweet. Its adding magnesium and throwing your cation balance off. You might start seeing calcium trouble.

 

[pickledLSD]

Those measurements were per gallon. I did have a little chart around here somewhere that I used to calculate my ppms. I'll have to find it and check that link out.

Blackvelvet:You're saying that I should mix 15ml PBP Bloom and 5ml CalMag plus with 1 gallon of water and use every watering? I also have Liquid Karma and Sweet, should I just rotate those into the mix in small portions every so often?

 

[Blackvelvet]

Yes, fert with every watering. Make sure a bunch of runoff occurs when you apply the ferts. This will prevent salt buildup.

Potassium, calcium, and magnesium all compete to get in the plant. Like a race or picking colored marbles out of a bag without looking. If your using pbp bloom for soil and the cal mag plus, your pretty balanced. When you add the magnesium from the sweet, the chances of the plant getting calcium lessen and chances of getting a magnesium molecule increase. So, a calcium def could occur. Potassium def could also occur but since there is so much, I doubt it.

If you want to add sweet, 1 teaspoon adds about 25 ppm mag. You should add double the calcium. About 1/4 teaspoon per gallon powdered gypsum could do this. If you find calcium chloride in a bottle, get net weight and % calcium and we can come up with a rate to use. Calcium nitrate at 1/4 teaspoon gal could be used but adds nitrogen. Forget the hastle and just try the cal mag plus and pbp bloom soil.

My only concern with pbp is that it contains alot of phosphorus. So much that it may build up in the soil and cause a problem like zinc deficiency. Best thing would be to use a nk fert with no p maybe every third or fourth time you fert to give your soil a break. Pro growers use a combination of calcium nitrate and potassium nitrate. peters 15-0-15 is a store bought version. Adding some epsom to keep a balance with this might be wise. 13-2-13 peters is like this with added mag. This is just some advanced growing thoughts you might consider in future crops.

 

[Blackvelvet]

If you choose sweet + some sort of calcium source, you would not use cal mag plus. Just wanted to be clear.

 

[powdergreen]

looks like the heat could be causing some of the curling leaf, and maybe a low RH could be contributing to a K def especially if you have too much mag and or calcium.

 

[pickledLSD]

The temperature never gets out of the 80s but I lowered it a little just in case. The RH never gets below 35% and it's usually a good bit higher when the light is off.

I watered tonight with 10ml PBP bloom for soil mixed into 2 gallons of tap water with a PH of 6.2. Next watering I'm going to try 10ml PBP bloom and 3ml CalMag plus per gallon and see how she likes it. Here are some pics from tonight.