To further the conversation, most people who switch off to a plain bloom fertilizer when they turn the light back to 12/12 will have early yellowing- pot plants use a lot of N, more than most plants. Today's bloom fertilizer don't have enough N in them so you have to supplement a bit for a few weeks.
Here's what I do. The first two weeks of flowering I continue to use veg fertilizer. Then in week 3 and 4 I use veg/bloom at a 50/50 rate. Then in weeks 5, 6, and 7 I use just bloom fert. The last two weeks nothing. I should also mention I always use a cal/mag additive, currently Botanicare Cal/Mag at 10ml per gallon since I use r.o. water. If you use regular tap water, 5ml should be ok.
Below is my current grow of Green Poison in flowering.....see, no yellowing in flowering. I have a current G.P. grow going on RIU if you want to follow it along, it may be helpful.