Potential fin rot? Even if the parameters seem fine?

Cycled - yes
Filter - yes
Heater - yes, current temperature is 25.5 C
Ammonia - test shows 0.5ppm but my tap water comes out exactly the same.
Nitrite - 0
Nitrate ~5

Hi there, I've had Gliese since December in a 95l planted community tank with some neon tetras, corys and snails.

Her fins are starting to look a little jagged and I'm wondering why. She eats well twice a day, her behaviour is just the same, and it doesn't seem to cause her discomfort, but there definitely seems to be some deterioration going on.
Any suggestions would be really appreciated,

Thanks in advance

Are you talking about the anal (bottom) fin?

How often do you do water changes and how much do you change?
How often and how do you clean the filter?
Have you used any treatments yet?
What do you feed the fish and how often do you feed it?

That betta looks really bloated