Hi! I have a female German Blue Ram and a male. They have been in the same tank for almost 1 year. The last 2 days she tends to stay at the bottom of the tank and does not swim, except when I put food on the tank and she rushes to get it, and then returns to the bottom. She avoids the male and hides as soon as she sees him. She is not bullied by any other fish in the tank, but is chased by the male in a gentle way and the male does not shows aggressive behavior at all. Water parameters are correct. What could be the cause for this behavior (staying at the bottom of the tank and not swimming around)?