Edge of leaves brown, any help will be greatly appreciated!

I bought two clones from my clinic with intentions of making them both mothers, but one of them seems to have caught something. The other clone is doing very well and is taking off. My plant is in a 5 gallon DWC set up with hydroton. PH balanced with vinegar (5.5.-6) and my PPM is about 200-230 (FloraDuo)

Anyone have any clue what it might be? Thanks!

Are your lights the same distance from both plants?

Depending when you got your babies, they're adjusting to your brew (maybe 2 different strains?). Give it a week. Symptoms continue, toss it... a clone is a clone. $7-20 is well worth the ounces you can grow with it.

About 2-4 inches away, im growing with 2x26 watt CFLS per plant

Maybe this will help?: http://www.marijuanafertilizers.com/marijuana-plant-problem-solver.html