Not all strains grow rapidly during the whole course of flowering. Some do hit slow spots.
If they are not eating at all in flower they wil not last long at all before everything falls apart. The demand on the plant is not less in flowering. SO, if you notice that they are not eating, and yet they are still looking okay except for the slower growth then they are still geting nutes.
You chould try a flush to make sure that you don't have complete lockout.
Check your roots... Healthy white eat the most.
Keep your humdity down to encourgage then to drink.
Room tems in the high 70's. Res temp in the high 60's.
You should be fine. Are they still taking in water? If they are taking in water and the ppm is not shooting through the roof then they are eating as well.
If every day your ppm level is going up then there maybe to much nutes in the water.
If every day your ppms go down then there maybe to little nutes in the water.
If every day the water level goes down, but the ppm stays the same, then you may be at the ideal ppm for your plant.
I hope some of this helps.