You have to remember that when you switch your lights over to the 12-12 cycle that the plants are still transitioning for 7 to 10 days from veg to flower mode, so you may want to wait about a week into 12-12 to start your bloom nutes. And yes, I would bump them up, but I know that all don't, that is just my preference, all though I don't start off at a quarter strength I start off at about half strength or a little more.
Adieu