Somebeech: Variations in photo period happens naturally. The length of sunlight changes a couple of minutes every day, increasing each day throughout the spring until the summer solstice, then backing off again until the winter solstice. Plants have had a lot of time to evolve to this cycle, so a few minutes difference each day is not stressful. But if you manually change this and are not consistent, then the plant will feel the stress. For example, if a plant gets 12/12 one day, 11/13 the next day, 14/10 the next, and so on, this inconsistency will stress the plant and most strains will morph. Depending on the strain, morphing can happen in as short as 4-6 days of inconsistent light period, but is usually longer. So if you must manually manipulate the period of light then you must be there every day at the approximately the same time. A couple of minutes difference each day will not be stressful, but forgetting for an hour (or even less) a few days in a row, or a few days each week, can cause a problem.
As to the revegging that is being mentioned, I guess I'm missing something. Are there other photos than the ones that were posted when this thread was started? From what I saw it looked like the tops were still flowering, just a little weakly which is to be expected in a window sill grow? If the photo period is 12/12 or less light per day, then most strains will not go back into the vegetation phase.
3rdeye: To answer your question about what to do about revegging - change the light period back to 12/12 of less... After a couple weeks they will switch back to flowering. But if the light period never went above 12 hours then I really can't see how they would have flipped into the vegetation phase anyway...