This is the air pump I have for running 2 buckets. I have the other 2 ports hooked up to the top drip. I definitely could add another airstone. Is this pump too weak with just 1 stone?you might want to try to add either a bigger airpump or another air stone. even if the water level is too high, if you have enough bubbles in the water, it "shouldn't" be a aproblem with the water level above the netpot.
something to try on this grow or for you next run.
https://www.amazon.com/Active-Aqua-Air-Pump-Outlets/dp/B002JPEVMC/ref=sr_1_1?s=lawn-garden&ie=UTF8&qid=1518468206&sr=8-1&keywords=Active+Aqua+Air+Pump,+4+Outlets,+6W,+15+L/min