Hey bro.... Sorry i forgot to respond to this one man..... What are u trying to reveg?
If its a plant going back to veg after from harvest.. Yea u can do that...
U can reveg flowering cuttings that clone back to Veg
Just do a water change and go 1/4 strength VEG nuts. Put ur lights back on 18/6 and u will be fine... It takes longer for plants to come out of veg in any system but u should be right back up in running in 3-4 weeks ready to cut agin or put back in to flower.