In terms of your question, this is a current, working example of feeding in coco... 2 gallon pots, fed 3 times a day in flower, 1 gallon of feed per water. In your example you have almost 7 gallons in pot size and you're feeding less than 1/2 gallon per day. The big pot will be your challenge, in terms of managing how wet or dry the plant remains from feed to feed. The thing is, you don't want the coco to dry out...none of it...otherwise, when your plants grow into the dry coco it's going to cause you issues. So you'll have to keep the pot pretty well moist, but not let it get stagnant either...it's a juggling match for sure. I've up potted during your same time in flower without issue, but never down sized...which I would think would disrupt the plant too much, so you may just need to ride this one out and take notes for the next run. Good luck.