Hello, i looked some pictures over google. But i cant dedice to problem. 3th week of plant. 250w mh light nearly 22hours open. Plagron lightmix soil with extra perlite. i cant find good quality ph meter. So im not sure from ph. Lastly i didnt give it to any nutrients till yesterday.first time i gave advanced nutrients connoisseur grow a+b yesterday.
I does look kinda like a pH issue or maybe mag deficiency. Hard to tell, the three finger leaves could be a sign of some other stress. I've noticed a few grows having problems in Plagron soil, maybe it is lacking something or improper ratios. Did you feed the nutes at full strength? I would start at 1/4 the recommended dosage, the plant is still pretty young.