Cookies is showing phosphorus D
I don't think that is a deficiency. I think it is light burn. I had the same problem on my first run with COB's
I usually grow with HPS. The last year Blue Cheese in 8 x 4 tents with 2 x 600w HPS.
Been following Growmau5 and the rest for a while now and decided to give it a go.
Basically copied Growmau5 32xCXB3590 at 700ma.
I thought light burn was only because of the heat from the light but i was wrong. As i could feel very little heat from the COBs
i placed them around 12 inches from the canopy and after a just a couple of days all the plants were severly burnt as in the left of your picture. Notice how it is only the ones on the left (closer to the light)
I think the high intensity also burns the plants. Mine looked just like those on the left and got a lot worse.
I also thought it was a deficiency but the other tent was fed exactly the same and had no problems.
I could be wrong but i thought i had to say something in case it happens to you again.
Just about to try again. I know COBs are the way forward. Just hope i get it right this time.
Gonna keep them at least 24 inches away this time.