most of the time though when they have external parasites they flash against rocks, wood,etc. Are your angels flashing any or are they just shaking....my discus shake their fins at each other as sign of dominance
Their shaking, not flashing. I've seen them do courtship displays and dominance things, but this is different. They just randomly shake their fins, especially their caudal fin. It looks like they are trying to shake something off. They have been doing this for the last couple of weeks, but before then they never did it.