Honestly if they drooped when the lights went out they are trying to tell you something. I run 24's until they're around 16" tall.
As i said, I start in the flexi plugs. Once their rooted i Transplant into the 16oz Styrefoam cups. Give them a week to get used to their new home with pure water then begin to slowly introduce some nutes. I use Ionic Grow, Ionic Bloom, and Ionic BOOST. for every Gal. of water use 4tsp of grow. So do the math but start slow. You can fry them if your not careful. At around 8-9" (or when I feel they need to) they move to their final medium. This being a 5 Gal. Grow bag trimmed down to around 10" high. (i do that because those bags are great, Cheap and easy to store but they use a TON of dirt). I slap em under HPS but continue the 24/0 until the get their first topping. (uses a lot of power but its as close to real sun as they can get inside which would be what they want) 3-5 more days of 24/0 to allow them to recover from the "raping" then its time for 17/7. This "veg" time is where your going to see some serious growth. I have one that grew 3" in a night. Make sure you've got the room before you let them get to big, Remember they can very well double or triple in size by the time all is said n done.. Give them all the water they ask you for in this phase. And alternate feedings with some water in between. As I said before just dont overwater. Once you get a few weeks going on 17/7 you'll begin to see the Pre-flower begin. If their to your desired height and there isn't a "Dick" in the bunch, bloom that bitch.. Just make sure you've got good Calyxes to give you those sweet sweet buds.
