Dead betta, please diagnose death.

[a guppy fan]

Today, one of my miracle bettas died in my 15 gallon community tank. He had only been 4 months old.Please diagnose death.
p.s how to deal with dead fish?
oh, and he did not jump

 

[Tacocat]

Today, one of my miracle bettas died in my 15 gallon community tank. He had only been 4 months old.Please diagnose death.
p.s how to deal with dead fish?
oh, and he did not jump

Please clarify: community tank? What fish and parameters please? Is it planted? Did it have hiding spots?

also what do you mean "miracle betta". Did it die and come back?