Your in the same boat as me right now the only thing I have going for me is I did not flip them yet I have been on veg time for almost 8 weeks, 2 out of the five I had did fine the other 3 not so much, so I made the decision to keep the 2 healthy ones and maybe veg for couple more weeks to maximize yield potential. I think a couple of days is fine to switch back to 18-6 but three weeks might make them reveg and or hermie on you. This was my first grow I had this happen so close to flower, and I still dont know why. What strain is yours again?