Discoloration and curling downward

Having a problem with leaves curling down and slight discoloration on the leaves. They are15 days old and about 3 inches tall with 3 leaf sets. In 5 gal pots with sunshine #1 , extra perlite, added bone, blood and kelp meal. Also garden lime and Epsom plus. All amendments made by "organic traditions". I am starting liquid nutes at low strengths soon . They're under a 1000 watt hps and 4+ feet from the light still. Temps 75-84. The leaves started discoloring on day 8 and now are curling down wards , or drooping, a little bit. It's discoloring is not yellow or brown, but kind of gray, more like a lighter green , kind of splotchy , as if the leaf is just losing color. It's only a few of them, the other ones are same size with no signs of unhealthyness. I can't check my ph yet until I get a tester bc mine is not working right. I'll get a pic up ASAP next time I am there.
Does anyone have any idea of what could be happening
Thanks in advance for any help

You can get this paper, not sure how to spell it, litmus paper. It's used to test ph in soil. The last time I bought it, amost 30yrs ago I got it from a drug store.

Thanks, good idea . I'll pick some up tonight If I can find any. I remember using it in school