LOL,fights actually break out over this stuff.Take some time to walk around with the guitar near the mics,amp e.c.t.heck,do a lap around the place.Try to find the cause of it.If it really is the mics close together or something else then don't hesitate to show them.
If you really can't find the problem,then you can still eliminate it through the use of a feedback suppressor...a cheap behringer shark thing would work fine probly.
Try once,fail twice...
