On Wednesday, November 18, 2020 at 11:22:01 AM UTC-5, badgolferman wrote:
One of our toilets has a slight leak into the bowl. The bathroom is
attached to the bedroom so during the night I hear the tank fill itself
back up very quickly. I have swapped flappers with the other toilet
and even bought two new flappers. The first flapper was a Korky but my
plumber friend said it was for other model toilets and I needed a
Universal type Korky for the Universal - Rundle toilet in question.
The toilet still leaks despite the new flapper. Do I need to replace
the flush valve now? If so what do you suggest? Any gotchas to be
wary of?

Sounds like that is the best option now. Replace the whole assembly, they are cheap
and it's not that hard to do, unless I guess if bolts won't come off, etc.