I had a tequila sunrise Delta guppy. I had bought 3 originally to add to my tank of German Blue Rams as they were a recommended tank mate for them. 2 died within a day of having them about 2 months ago. The 1 remaining was doing so well until one of my gbr got territorial of one side of the tank due to him and the other fighting after discovering both were male. After the one became aggressive he will chase anything from that area of the tank he has deemed his. But I never really seen him nip at the guppy but just run him off to the other side again. I came home from work and after relaxing for a few I went to feed my fish and seen the guppy laying on a fake plant dead with his back fins looking shredded on the ends and his pectoral Fins sticking straight out and mouth wide open. I inspected him further and seen nothing that looked like an illness. I checked over the other fish and they seem fin physically as well. I don't understand why he died suddenly when he was okay this morning and afternoon. Should I do a water change now that he has been removed from the tank? Or anything else I should do?