My guess is that the problem may be related to watering. If the water drains through and then gets sucked up by the plant, you end up with residue that mixes with the new feed and throws the balance off. Either top water or bottom water, not both.
@Mañ'O'Green put together a great watering guide that I follow. I use Floraflex flet pad on top of the soil to slow my watering down and better distribute the water. It takes me 10-15 mins to water but it def soaks in.