Stealth Hydro Box

Hey, I have the Stealth Hydro reservoir and had two questions. I germinated seeds and put one in each rockwool cube. I understand the air pump should be run continuously but what about the feeding tube? The rockwool is starting to turn brown where it meets up with the tube. Any ideas on that? Thanks.

after the roots hit water, you can put it on a timer at 3 mins per hour.. or just run many more air stones.. works both ways