Switched to LED, now plants are suffering

[NedFlanders]

So I recently changed from 1000w HPS to Mars Hydro FC6500 and FC8000 and am now getting crispy leaves. Temps are a little higher than before but I understand that is ok with LED? I haven't change anything with soil or nutrients.

Well water starting at 120ppm.
Pro Mix HP, Floranova Bloom at 6.5 ph, 600ppm (500 scale) every watering.
Runoff has been around 6.0
Temps and humidity is in the pic of Pulse monitor
I've been running this for years and just switched to LED.

2 large Plants are in an 18 gallon tote.
I'm sure to get adequate runoff every watering.

Could this be caused by heat stress, light stress or PH? I appreciate any replies!

 

[TPFTFW]

Spray 1/4 tsp of epsom

Worked wonders for my issues after switching

 

[NedFlanders]

I got some Cal-Mag, should I add a little each watering? Does this look like cal-mag issue? Wonder why just switching to LED would cause a deficiency?

 

[VerdantGreen]

LED light is pretty strong these days and most people find they need to use Cal/Mag or similar.maybe extra P in flowering,
Also when your plants are in veg a dark period can help reduce the DLI (total amount of light they recieve in a day) and this will reduce the issues.

 

[Koondense]

Check your VPD.
General rules with leds... higher temps, higher humidity, more Mg(epsom) and your plants will be happier.
DLI is also to be checked, plus light distance.

Cheers

 

[exploziv]

You need proper VPD and maybe more Ca and Mg as well..

 

[Entusia]

Since with proper LEDs PPFD is much higher than with HPS, and since you replaced a single 1kW HPS light with 1.5kW of LED lights, temps have gone up, etc a lot of grow parameters have changed.

I'd wager you'll need more than 600ppm total in your water at this stage with LEDs. That's gotta be at like EC 1.2-1.3 mS/cm now... I'd take them to at least 1.5-1.6 or even higher since you're in full bloom. Don't shoot it all up in one go though, go from where you are and incrementally add 10-20% more at every fertigation until you find your sweet spot

Cheers!

 

[wh1p3dm34t]

yea entusia is correct, it is caused by the leds higher ppfd, without a lightmeter it is very difficult to set the optimum

 

[NedFlanders]

Thanks all, makes sense. I'll gradually increase ppms, add cal-mag.

I'll adjust dehumidifiers to get closer to the ideal vpd. It's always a challenge because lights-on the a/c removes a lot of humidity but then lights-off humidity shoots up and dehumidifiers take over. I don't have a centrally controlled system, just several independent a/c's and dehumidifiers. There is definitely room for improvement and I will work on that.

The Pulse Pro has a light sensor on it--I'll take some readings and post them tonight.

I really appreciate the help!!

 

[Creeperpark]

You need to go back to HID lamp and finish this grow before switching lights before it's too late. On the next grow start with LED and use cal-mag with RO or Rain water.

 

[dimodz]

when you switch from HPS to LeD it be needs more Cal/mag as before ....

 

[buzzmobile]

Well water starting at 120ppm.
Pro Mix HP, Floranova Bloom at 6.5 ph, 600ppm (500 scale) every watering.
Runoff has been around 6.0
Temps and humidity is in the pic of Pulse monitor
I've been running this for years and just switched to LED.


Could this be caused by heat stress, light stress or PH? I appreciate any replies!

Consider dropping the pH of your nutrients to 6.0 and CalMag is a must under LED.

 

[Three Berries]

I went through this and my problem was inadequate Ca.

 

[VerdantGreen]

Ive found that, as an alternative to cal/mag, in organic soil i am adding 4g/litre of soil Gypsum and 2g/litre of soil Dolomite lime. That seems to keep them nice and green.

Ive been using LEDs for 10+ years and this problem has only come about in recent years as LEDs become more efficient and brighter.

VG

 

[Creeperpark]

It's not a good idea to change anything major during a grow. If you change water or new soil with transplant or lighting while the plants are flowering, you can shock the plant and lose weeks of vigor and sometimes lose all vigor. If you try to fix the problem with just cal-mag you may be very disappointed. The plant's metabolism can't make changes overnight because the plant's chemistry is already tuned in to HID or HPS lighting. That would be like taking a plant from Mexico and taking to Canada and growing it. The switch will cause you to lose time and yield.

 

[GMT]

Yeah I suffered switching plants from hps to led. Led all the way is much more forgiving. I'm adding hesi boost all the way from switch to week 7 now. It's not sold to be used that way, but it does help.

 

[GoatCheese]

Thanks all, makes sense. I'll gradually increase ppms, add cal-mag.

I'll adjust dehumidifiers to get closer to the ideal vpd. It's always a challenge because lights-on the a/c removes a lot of humidity but then lights-off humidity shoots up and dehumidifiers take over. I don't have a centrally controlled system, just several independent a/c's and dehumidifiers. There is definitely room for improvement and I will work on that.

The Pulse Pro has a light sensor on it--I'll take some readings and post them tonight.

I really appreciate the help!!

Use a timer on your exhaust fan so that it isn’t ON the whole time during lights on, it helps alot.

You have to change the on/off times depending on the season but during cold/dry season i had my small tent’s exhaust run 15 ON- 60min OFF and it’s a massive help to keep RH% even close to where it should be in the winter times up here in the North.

..i have a circulating fan in the tent that is always on even when the exhaust fan is off.

 

[Petrochemical]

Ill use banana peels

 

[f-e]

You have doubled your light.
What space are you in. I can calculate a rough PPFD from the light output and space it's spread over. I need it in metric though.

I have no doubt you need to half your light before doing anything else. The math is just to prove it. Half the light, look at RH.

 

[heatherlonglee]

I recently switched to LED from HPS/MH Blue. Only thing that changed is that I need to water one day sooner now. I used to water every 5 days now its very 4 days. In a few photos the plants look thirsty to me. After being 100% sure you're not in a over watering situation; I'd say start watering one day sooner.