Clownfish not eating much, twitching, swimming vertically and staying near bottom of

Hi! We have a clownfish of 6 years and she's been acting strange lately. She has a mate (who survived ich 3 years ago) who's trying to 'snuggle' and mate with her. Problem is she doesn't want to and she hasn't been eating a great deal, has been twitching a bit (sort of like she's in a spasm), swimming vertically and in a pattern and staying near the bottom of the tank. The only problem we know of is high nitrate and we recently had a problem with high salt (but that is resolved now). Recently, we had a yellow goby die, he wasn't eating much and was quite old. We're not sure whether they are connected but would hate for the clownfish to have the same end.

Any help would be much appreciated!

P.S. The 2 clownfish are the only fish on the tank as of now.