I didn't realize before that you were using miracle grow soil. that already has fert in it, so I'd suggest you avoid ferting for a while and see how things go. this contradicts what I said earlier, but I overlooked the name of the soil. If they yellowing continues after not ferting for several days, then you might consider giving a dose of fert. it would be nice if you could post once a day with pics so we can see what's happening.