URGENT, Has anyone heard of this.PLEASE HELP!!

I have been having a problem with my 4 girls since going into flower. It looks dead on like Zinc in the Growfaqs, but I am using fresh Flora-nova. But a new wrinkle has developed. The leaves closest to my air cooled 600w are yellow but leaves hidden by the bigger leaves look normal and shoots farther away like way further away don't look bad at all. Temps are in mid 70's always and ph has been below 5.5 but have been brought it up to near 6. Is it possible the light is too much for a 4'x3' and 8' high. This is a digital ballast and the hood is cooled and the glass never get more than luke warm. 4 more weeks to go but the top buds are shriveling and it is spreading. Please help if you have heard of too much light or if you need more info. Just bought this light and now Iam wondering if it is too much! Thanks

Is that the first time you are growing in that space?
Any pics?

Sorry no pics everytime i try they just look blurry but if you look at zinc def. in growfaqs that is exactly how they look. This is the 4th grow in this space but the first with the new light. Easycool6 hood with digital ballast and sunmaster 600w. Hood is aircooled So Iam just confused by the plants problems.

how close to the plants is the light?

if the light is too close to the plants it could light bleach them... even if the plant isnt hot... compare it to a sun burn from us... even though it might only be 80 degrees out the light rays still burn you... same thing can happen to a plant..

We are going to need pics What light did you use before? How did the last four grows go, any problems?

I finally in my big stupid head have come to the realization that it is getting some kind of bleaching going on here. So yes Simpson, I believe you maybe right. Began noticing it is only happening close to light. Have moved the light a good foot from tops and smaller growth probably up to 2 feet. Did this 2 days ago and believe it is helping. I just thought with a air cooled hood you get it as close to the plants as possible and with glass protected hood I thought space and distance would be less! Well live and learn. Unity, Before this I used a cheap 400w open reflector from HTG. It was under 200 bucks and it worked good. I just get such huge short plants I wanted something to get through the canopy. Last time with the 400w the canopy got so dense I tried trimming old fan leaves. Didn't like doing that. My last grows have been great. Thanks to all and I gave reps.