Yellow/Brown Spots

1000Kw HPS bulb
temperature 80F. Daily 90-95F spike for 2 hours!
PH 6.5
Growing medium - Coconut fiber
Nutrients: 2.5ml each of Alg-a-mic, Bio-Bloom, and Bio-Grow
Well ventilated
Extra CO2 using yeast-sugar-water

My plant is starting to get brown/yellow spots around the edges, which may be replaced by a small hole/tear where the spot was. Picture attatched.

Only a small percentage of leaves are affected are found towards the top and middle.

Any suggestions on the problem? Does not seem to be burns from the lamps. No PH problem. I have recently heard that Bio-Grow may not be suited for coconut fibers?

Appreciate any help :thumbsup: