I'm glad to hear of your fishes recovery but keep repeating the whitespot treatment every 4 days until all the spots have gone!
Yes, it sounds as if it's breeding behaviour that's causing the exhaustion & fin/tail damage. They can breed without showing any tubercles. I would take Jaws out of the main tank & give 'her'? a rest away from the other fish until you observe her looking better. Don't forget to keep up the whitespot treatment because fish can die without ever showing a spot.
Spawning takes place at dawn & lasts about two hours, you could set your alarm really early & have a look, see? Breeding is seasonal & depends on day length & rises in water temperature. The male(s) tries to chase the female into the 'shallows' to spawn.