My Electric Blue Acara has been "shivering" recently and she also occasionally flashes off of hard things in her tank. She's just tonight started to scratch her head off of the edge if a pleco cave and into the gravel. She looks fine, is behaving fine (personable and scraps with her sailfin molly friend all the time), and she's eating fine. The shivering has been occurring for a few weeks with the other symptoms being more recent. Any cause for concern or ideas why she's doing this?