Mine are behaving similarly I have 3. 2 are about 3" and 1 is about 2" they are with two baby green texas cichlids. If I moved them to a 75 gallon would I still have to get rid of the others?
They may well of paired up but not definate untill they spawn. As long as the third firemouth isnt getting relentlessly chased it should be fine. Leave them as they are.