If they're showing signs, you need to hit them HARD with nitrogen. They'll back out of it. Mine are vegging strong, high nitrogen feedings daily.
I've been feeding them so hard with high quality nutes (grow with a ton of nitrogen) and topdressing with a nitrogen based topdress.
This is strain based, the Chocolate Hashberry is said to start 10 days to two weeks before the others, and out of my plants, only those three are starting.
My point was more that transition time is very close.