Well for one, coco very hard to overwater unless when you were making the mix up you might have blocked up the drainage holes. Good way to check with your pots being so small you should enough space in the end for roots to grow through, that's the only it could overwatered. It's a more of underwatering cause your mix isn't holding enough fluid. Next time add coco husk or bark as this is better at holding water. Also, when u were doing your mix was the coco mainly dust or stringy with with of hush and that attached. Try lifting the pots a little up from the drainage holes so water can escape. And any roots that grow through will also drink run-off and your plant will explode, just gotta be careful with ph/EC as it's, it's mini DWC. Try that. Your coco should damp, put your finger down and if dry more than 1-2 inches down, it's too dry. Also if in a tent make sure u are sucking new air in to the tent either by wsy of extraction tbat will suck new air in or set up ur extraction fan to blow into tent and close windows, could be a factor of c02 too.Happy growing.