Since I've had a few autoflower grows under my belt I'd be glad to help out, I'm subbed
I've got a few questions tho. 1, Is there a particular reason you went with the miracle gro mix? I understand if $ is an issue but there are a lot better soils out there. Not doggin at all but just curious.
I've found through my handful of auto grows is that they grow and yield to their environment. Having used the same size pots before with some Short Riders and only got an average of 1/4 oz from each plant. Once I went to 2.5 gallon pots my yield went up to 3/4-1 oz. MY ADVICE to you would be to go to larger pots and reap the benefits. I'm growing 2 Jock Horrors outside in 5 gallon buckets and they're about 3ft tall and gonna give me a good yield, about 1.5-2 oz each is what I'm expecting.
Do you have the space to grow plants that tall?