If the pads still have plenty of meat on them, try re-greasing between the backing plates and pads. I need to redo mine now. They are squealing at low speed sometimes when I'm not even on the brakes. I do have Carbotechs on there so they always squeal when braking at low speed. It may have gotten worse because of my last track day, it was raining.
The cold weather can make them squeal more too.