As above. A and b together, definitely I'd be feeding more, unless you give huge amount of feed/ water, definitely lack of nitrogen, I doubt your in soil most likely soilless, there's a big difference, looking ok otherwise, what week you in? Indoor /outdoor?you don't need to check your medium ph or run off, you'll drive yourself crazy , it fluctuates anyway, try keep ph stable, 6.5 is best but if you do it at 6.8 keep it there stability is key, bring it down .1 each time to 6.5