you very well might have dry pockets, coco will do that if you don't wet it down good regularly. i'd suggest waiting till they're very dry, then set your pots in a bucket of water for a couple of minutes each, then set them up on something so they get a chance to drain real well. if you have any dry pockets in your pots, that'll wet em down and get rid of them.
coco is a strange medium, but very easy to work with once you get used to it. when your coco is fresh, it will absorb calcium and magnesium, so you have to add extra. Once your meet its deficit, all the sudden you don't have to supplement it anymore, you have plenty. That usually happens around the second or third week of flower, so about two weeks into flower, cut back on the cal-mag by about 75%. but, right now, you have to add a good bit.