When a plant is revegging, you have two choices:
Let it re-vegetate completely if you want the plant to be in the vegetative stage, or…
Correct the light periods by getting rid of any possible light leaks and giving plants 12 hours of interrupted darkness a day to get them to go back into the flowering stage.
NOTE: Plants that are far in the flowering stage can take a month or more to re-veg, while a plant that has only just started flowering re-vegs much faster. That goes both ways. If a plant has been re-vegging for a long time, it may take a few weeks to get the plant back to flowering and developing buds.