Fish died :(

[mollykid]

So I had a pineapple platy for about 1 year and it had got stuck in the filter earlier because of high ammonia but I cured it and had a mesh on the filter and recently it died yesterday the symptoms were it just kept sinking to the bottom of the tank , it would try to get up but couldn't I checked my water and all of the test were great , if someone could please tell me if they have any idea of what could have happened to it thanks in advance

 

[mollykid]

It had got stuck in the filter a month before but pulled him off right away