Your plants appear to be overnuted and about 2 weeks old tops. I can't really find anything that you are actually doing correctly so I'm kind of surprised they are growig at at all.....but it is a weed after all.

Ph should be between 5.6-6.2 in hydro......6.8 is too high.
Miracle Grow has no place in hydroponics. NONE. ..... you should be using true hydroponic nutes.

Best of luck to you ......honestly......you've gotten farther than I would have thought with hydro......but you're in for a nasty surprise at some point and I don't want to be involved in it.

Again....good luck. Really.