feeding with a passive wick system

So I've done a few outdoor grows nothing special. I've got a grow tent now with a t5 4 bulb setup and a passive wick system. I'm doing a clone of juicy fruit and the roots have sprung immediately. I'm using the FF trio pack and trying to follow the nuts schedule. My bucket holds almost a whole gallon of prescribed water with nutes. My problem is wondering what to do if the plant doesn't use all of the food before the next feeding?

Thanks