Help! leaves turning white/pale on edges and curling upwards

Sam Spade

Sam Spade

New Member
Hi Everyone,

I'm a first-time grower who has run into his first problem, about sixteen days into the 12/12 flowering stage.

Things were going well with my grow, but certain leaves, at different parts of the plant, are now turning a pale, white, or tan color, and the affected leaves are also curling upwards at the ends. Over the past three days, more and more leaves seem to be exhibiting these symptoms.

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Here is some basic info about my grow:
Master Kush clone
24" x 20" Scrog
Flood and drain (a.k.a ebb and flow) system, 5g upper, 18g lower
6x42watt cfl @2700
2x42watt cfl @6500
Nutes: General Hydroponics
Temp: 75
Humidity: 60%
Ph: 6.0 +/- 0.2
PPM: ~800-1020 ppm (right now at 900) (tap water I'm using has about 250ppm before nutes are added)

Does anyone have any idea what could be causing this? I really appreciate any advice you might have.
 
Update: I think I might be dealing with a magnesium deficiency, probably because the tap water I've been using is hard (>200ppm). So today I added 2 tsp of epsom salts (dissolved in a small pot of water) to my res, which was holding 8g of nute solution at the time (1/4 tsp / gallon).
 
Thanks Ganjahorder. My CFLs were about three inches from the plants.

But I don't think it's heat stress for the following reasons: 1) My CFLs don't get that hot 2) I have a thermometer at the top of the canopy, which holds steady around 75-80 3) the leaf damage is not correlated with distance to the lights.

I'm really hoping it's magnesium deficiency (as evidenced by what appears to be intravenal chlorosis), and that the epsom salt I added yesterday stops further damage. It's kind of too early to tell.
 
Update: Adding epsom salts seemed to stop the damage. I clipped off the twisted tips to see if any new ones came about, but none have since I've started supplementing my water with epsom salt.

Lesson for my next grow: Because I was using hard tap water, I suffered a magnesium deficiency which could have been avoided had I also been adding epsom salts to my water -- probably starting at the beginning of the 12/12 period.

Signs of magnesium deficiency: 1) leaves cupping or curling upwards and twisting 2) leaves turning pale or white, starting at tips and edges or in the spaces in between veins. This is called "chlorosis." 3) Affected leaves seemed older, but damage was not related to height, heat, or distance to my light source. 4) Adding epsom salt seems to prevent further damage.

My only question now is how much epsom salt can/should I add per gallon of water? I'm starting with water that is about 250 ppm.
 
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