I'm 3-4 weeks in from seed... 5 plants, 1 is struggling. 3 started with brown spots starting on the outer corners of the lower most leaves... I checked the pH, and dropped it from 7.8 to 6.0. This seems to have fixed the problem for most of them, except one. This one is growing unbelievably slower than the rest and seems to be sick. It only has 3 sets of leaves, all of which are light green with dark green veins, as well as the first set of leaves (the lowest set) continuously browning. I have a control plant, which is growing perfectly, so I know it's not the amount of nutes or pH... this plant just seems to be struggling, what can I do to help this one? Could this one just be a struggler? My control plant is a mother plant growing in a separate drip system. The others, are in a 4 bucket DWC central reservoir system, and are thus getting all the same nutes and pH. Why is just one plant struggling? All help appreciated, thanks.