so, if a crop in 12/12 was accidently exposed to an extra 20 minutes of light, it should only cause very minimal stress, right?
It's not ideal but I really dont think it's going to hurt terribly. I did the exact same thing several days ago. I left the supplemental cfl on about 20-30 minutes longer than the primary light. Didn't hurt a bit as I can tell. Mine are in their 7th week of flower though.