It is possible that the fan leaves that you are pulling off are naturally dying. That isn't a sign to stop feeding. Are you certain that the signs are of over fertilizing? A third dose of nutes per day at this stage should not be causing over fert, unless you are feeding them more than once in a day! We are having fan leaves at the base of the plant changing to yellow and shrivelling up from week 3 till the end. It is an indication that the plant is no longer vegging and is using all its nutritional resources to produce flowers. I'd never use leaf changes as a guide to harvest. You should keep feeding until 1 week before chopping, then flush with water and/or final phase for the final week. Don't chop till you are at least 4 days beyond being sure, and don't base your assumtions of what your final smoke will be like on a bit that you cut off earlier. Big changes can and do occur throughout bloom cycle, and bud with fert in it tastes different to proper clean bud.