Red Fire Goby behavior

I had a school of 3 fire gobies and they all seemed happy together. After a recent 10-hour power failure I seem to have lost one (although I never recovered the body). The other 2 are now starting to fight and I can see some tail and fin damage on the smaller one.

What should I do?

Get more and make a larger group - was thinking of making the group 5 strong

Any advice welcome

What worked for me was I sumped the bully & rescaped a bit & reintroduced it & they were fine...