That's just their breeding mode.
I'd say its typical for males to go off feed during breeding season.
Females don't usually go off feed until they are closer to ovulation,but every female is different.
I have one female who stopped eating after she started glowing , and another female who seems to be eating more than ever since I've tired pairing her with a male.
I still attempt to feed them cause even if they won't eat there's someone else who will.
The females are probably better at retaining weight during the breeding season as its mostly going toward follicle/egg development. As for males as long as he was healthy at the start of breeding and doesn't loose any significant weight he should be fine.