Only one platy is at the bottom of tank all day long

[jclv]

Hi everyone. I have a question if some experts can help me here.
I have my fish tank already more than a year, of course all is cycled and my parameters are always a high priority to me.
Already checked all main parameters, ammonia, nitrites and nitrates. Also PH all under ranges, as I always had them all along. All my fish have never been sick and I am very careful with my maintenance.
Although, i have noticed that since almost 2 weeks ago, only one of my male Platys stayed at the bottom of the tank like if he is agitated or breathing very fast, and when I am gonna feed them, he comes right up to eat just a few bites and then he goes back at his corner and remain there almost all day and night. The rest of my fish are fine. Also, none of the fish have ever picked on him, so I know for sure he has not been bullied.
Does anyone have any other ideas of what this could be please?
Also, it might be worth to mention that he is the only one who is currently father or dad of 8 baby fry i got in the tank. The mom is perfectly fine.
I would really appreciate your help guys.

Also, the first picture is from his "wife"
The mom of all his children

 

[Goldfishexxpert]

I’d assume it’s a problem with his stomach or gills, make sure there is nothing in his gills and maybe check if the temperature is too hot or too cold for him, if he’s uncomfortable with the rocks I’d get that changed, maybe he doesn’t have enough room and he’s becoming stressed, notice those little things, I’ve never had a fish who’s done this out of my 4 years of owning multiple fish so I worry as well, just keep an eye on him

 

[jclv]

Thank you very much for getting back to me. I just found the correct diagnosis yesterday, so today I will try to start to medicate him today and see how it goes. In case it works, i will post all progress so we all learned about this. Thanks a lot