Red Platey Acting weird

[Katielady0501]

My red platey is acting weird, he sits at the top of the tank, not swimming and won’t eat. The others are doing just fine but he isn’t. What could be the cause of this?

 

[itiwhetu]

How old is this guy

 

[matthew12098]

What are the water parameters of the tank? How big is the tank? What other fish is he with?