what causes a plant to reveg?

Hi everyone. I was just looking for some info on the subject. on my last grow I had 2 of my 3 plants reveg on me and I dont really no why for sure. the two plants also started to hermi late in the flower period. their was never any mishaps with the light schedule that I know of. the only things I can think of are heat stress cause my temps got out of control a couple of times it reached the upper 80s. also we suffered a power outage during the night cycle. it didnt interupt the lights at all but I run a dwc setup so the air supply was shut off for about four hrs. any thoughts would be great. thanks.

Oh, thought you were needing to know how to REVeg a plant..

my bad.

what causes a plant to reveg?

Interupting the light cycle so that it gets less than about 12 hours of uninterupted darkness per "day".