Sounds like you need to add Nitrogen. I just feed Veg nutes for one or two feedings @ week 3 or 4 if it's turning yellow. If it's starting to yellow and I'm passed 5 weeks I let it go and accept my yellowness.
I am going to assume that you switched to flowering nutes the day you switched the lights to 12/12? Well I have found that the plant uses up a TON of the stored Nitrogen for the stretch phase of flowering. I keep it on veg nutes for 1 -2 weeks into flowering (depending on how long the veg was, the longer the veg, the longer I keep it on veg nutes, typically larger plants).
Hopefully you aren't rootbound and some veg nutes will help ya out.
Good luck and happy growing!
Ohh and don't listen to douchebags, they always hijack threads with their bullshit. Some of the people who've been here awhile get into debates with them and your thread loses track a little. Just ignore all of it.
