ok, well, i thought about this yeaterday. pics of your roots are different to me. for example....once some roots emerge from pots they usually jusp right in the water and then the other follow. your all seem to be getting near your water and stopping. they should be longer than that by now. i do see some nute burn..just use tiger bloom, and get some real nutes from the hydro store. get some flora nova. never did me wrong yet. if i were you i would do a res change. clean water, 1/4 strenght nutes, and then maybe drop your ph a little. 5.5, 5.8. they look healthy, and so do roots, but for some reason your roots are keeping there feet out of the water, like they dont like it. the bursting bubbles are keeping them happy. no reason to panick.