Based off of that it could be:
1)PH Lock Out from salt build up?
2)Low Iron/Mg or probably Nitrogen if yellow / golden brown
3)High heat in 85°F to low 90°F ranges
Or most probable spidermites
but yes yes def put up a pic
Many strains do fade to pale yellow on the fan leaves with energies diverted to the buds, and its always a good idea to flush the system once vegging is done ...did you?
post a pic...or let the blind lead the blind ....lol
imo---ur plants were starving for N when u flipped to flower---it would not be too late to give them a bit now being sure not to feed too much as N is not a primary nute needed for flower---cal mag may also help
if u in hydro results s/b seen in a couple days---soil a couple weeks
I was not aware a plant needs a lot of (N) approaching bud(seedset?) ..the plants concern male or female is to reproduce, it certainly don't need (N) nitrogen for that, but quantities of (K) and (P) is ideal, to make the energy for this it needs those fan leaves as solar sugar engines, consider if possible returning your plants to veg, for perhaps another month or two, just to grow some fans, or even re set the rootzone some?
Again without a pic ...its blind leading the blind
i use 10-10-10 till the last couple weeks and have never had a problem. like everyone said pics will help. if you had spider mites then you need to handle that first then you can do the feeding that you need to help the plant. get you some safer 3n1 and get the mites. i have never used this stuff as i'm on a budget, but a lot of people use it till finish. no matter what you use to get the mites you need to clean you space with bleach/water or 50% water 50% alcohol in a spray bottle.