yellowing new growth

i have 5 clones growing in a 4x2x8 closet. i have them in 3 gallon pots and under 1000w hps light which is about 4 feet above the plants (too high i know) and will be lowering soon. the temp is around 80 degrees with the humidity at 40ish. they are about a week old and one one of the plants the new growth is coming out bright yellow and spreading outwards to the edges of the leaves. this is my first indoor grow and i am curious of what the problem could be. is it a nute deficiency, lighting problem, or ph issue? just got a ph tester and will be testing the soil tomorrow. any advice would be greatly appreciated.

Using fox farm ocean forest with a little extra perlite BTW