Stop using the miracle grow IMO. I had this same problem in my indoor hydro setup. I gave them a dose of cal mag and a half dose of superthrive and they bounced back.
No longer using miracle grow, for a few weeks now. From start to flower i was. But yeah no go on the miracle grow, just low on funds. Just picked up cal/mag plus ill get some superthrive and see how it goes. Thanks
looks like phospherus def. to me, maybe the MG was lockin you out...ever flush?, maybe try raisin that pH from 6.0-6.6, to 6.5-6.8? cal-mag always nice to have, with fox farm expecially it seems...good luck bro