If you want them to bloom, to go into flower, why would you switch back to 20/4, especially since they are autos? The point of growing autoflowering plants is so that you don't have to worry about switching light schedules. I've never done an auto myself, but as with any plant, switching light schedules constantly will most likely put some stress on the plants.The only reason I can think that you went to 12/12 is that they weren't flowering automatically and you tried to force them, but now want to give them more hours of light to help speed up growth. Sounds sort of like forcing flowering to determine sex, then switching back to veg to attain more size, which isn't really harmful, but does induce some mild stress as the plant gets confused as to what it should be doing. Like I said, I've never done autos, but from what I've read, there's no need to change your light schedule.
