phantom power problem?

[mapex78]

I was doing some recording tonight, and i nopticedth the 001 was introducing a hi end hum and remarkably reduced gain on the 2nd channel. channels 1 and 2 in my setup are powering large condensers for overheads on a drumkit. I was able to get rid of it by turning off the phantom power and turning the channel pot all the way down. I then put everything back the way it was and it was gone. Problem is it showed up about 20 minutes later, I went through the same routine, and it hasn't shown up since. But i am sure it will probably show up again. ANY IDEAS???//

Thank you