I have put, and still put seedling in MG soil, and use either MG or FFOF. Whatever MY bank allows. FYI My Seedlings in MG, all 3-3 Sprouted, and now are doing great! But that is just my luck. What nutes are you using? I use FF nutes, and Noticed that when I feed them That the PH goes up a lot faster, than when its in FFOF.