What deficiency could this be ?

Let me know what you think.... temps are a little low at night !!
Using Floranova bloom going into week 4 !!!!
PPM @ 1100 first week of flower
PPM @ 600 first week
PPM @ 700 week two(first sign of deficiency)
PPM@ 800 week Three leaves started to canoe
PPM @ 1100 first week of flower !!!
Temps at 74 lights on and 62 lights off!!!! Humidity is at 50%
Lights are 15 inches away 600 watt MH

Having similar probs in soil, have 600hps in tent, well ventilated, various strain, at varying stages, I usually add 4 when I harvest 4... Anyway the problem seems to affect all plants in tent even though they are not all having same water/feed mix or volume. It is since the outside temp. Has dropped in last few weeks. I suspect it may be due to variation in humidity, the grow is in a small portacabin. As cold air enters and is heated by an electric wall heater which is thermostated- (and HPS bulb 12hrs a day) the relative humidity falls dramatically as temp. rises from say 5c to 23c, the air leaving tent feels humid enough but the intake will likely be low rH..... I have considered nutrients and lock out and flushed with water, ( the tap water here is ph6.8 spring water) I have had healthy results with the same nutrients and watering regime at same location in warmer weather. I can't just decrease ventilation because the Walls get wet with condensation as they stay cold these days so I don't have a solution for problem yet- changing to another location not possible........ If yr in a more stable environment you could perhaps control humidity accurately with ventilation, same for temperature......

This may or not be relevant to yr problem, I will watch this thread to see what others advise. I found very good photo diagnosis for multiple deficiencies just by googling relevant words...... Some posted on this site I think

nutrient burn...its not deficient...you can read those labels on your nutrient bottle as much as you want, but it doesn't tell you how much nutrients/water you are giving them...I see a big rockwool cube...you hand watering that or is it in a ebb/flow system or something?

The tips of the leaves are getting burned...simple as that...you are just perpetuating it by giving it higher nutrient contents...

massah said:

nutrient burn...its not deficient...you can read those labels on your nutrient bottle as much as you want, but it doesn't tell you how much nutrients/water you are giving them...I see a big rockwool cube...you hand watering that or is it in a ebb/flow system or something?

The tips of the leaves are getting burned...simple as that...you are just perpetuating it by giving it higher nutrient contents...

Click to expand...

I agree with the massah!

Yep, you need to back of on the nutes some. I would flush if you haven't already, also check to make sure your light is not to close to the plants. You should be able to put your hand under the light with no prob.

That, my friend, is a Cal/Mag deficiency. I had the same problem my first 2 grows, Add some Epsom salts (1 tbsp/gal) every other watering. The necrotic areas will not come back, but new growth should be good.

Sorry Massah and Chem Dawg. Thats what I thought too at first, and damn near killed off my entire grow before I finally listened to the cal/mag camp. It took my third grow to figure it out.

I'm with Harer...kind of. It's Magnesium. No doubt. I, too, use rockwool. They MUST be top watered and flushed every week. Nutes containing high amounts of K will inhibit mag uptake. The K mag balance is a tricky dance. In a way, everyone is correct. Excessive K can cause a mag problem. I would flush heavily. Then add Botanicare Sweet Raw. It's pure magnesium sulfate. Incoorporate this into your feedings. Mag problems tend to get worse deeper into the bloom phase. Also, make sure you cure your rockwool with a Cal Mag product, as rockwool tends to lock up the first few doses of Cal and Mag.

You can look at my thread a few pages back and see that I went through the exact same thing a while back. I had switched to a high K bloom system and went mag def right away. While the plants do not use alot of mag, they do need alot of it present in the medium. This becomes more critical as high amounts of K are added.

Good info CG!! I'm always in soil, but I have heard that about RW as well!! I think a mega dose of K in any medium is a bad thing.

hmmm. doesnt look like deficiency to me. The edges looked burnt. I could be wrong tho, I assume that how cal/mag def shows, the yellow leaf edges? I thought it was rust spots.
Not to steal a thread, but what causes rust spots on new growth?

@Pistol Pedro (and any others growing in tents):
What kind of tent are you growing in? Unfortunately many grow tents (especially the cheaper ones) produce toxic chlorine gas from the plastics in the cloth which will cause your plants to burn up. It doesn't matter what you grow them in or what you feed them they will always burn up. A quick remedy would be to keep the metal frame of the tent and throw out the actual cloth tent and replace it with some black/white poly or some other suitable material. Hope this helps for now!