Last go round with FFOF I had gnats coming out of the soil after the first watering, new unopened bag straight from the shop. Is it related I dont know but I am in the South.
I would most def. get the plant with mites away from the others if its not to late. Everything looks good for your first grow, keep it up & you will be rewarded!
You could flower the mothers right after taking the cuttings but a few days to recoup will never hurt. As for veg size thats a personal preference more than anything, ie- size of room & lights.
Also large swings in temperature from night to day can cause mold to show as well. Temperature swings of 20 degrees or more from night to day are no good, imho.