Hello Pappy,
So sorry for your loss.  The gasping could be lack of oxygen in the tank.  Do you have an extra aerator and pump running in the tank?  As the weather warms and the water in the tank warms up too, the water has less oxygen in it.   I WOULD ALSO TEST YOUR WATER TO SEE IF THE WATER CHEMISTRY IS ALRIGHT.

The bright red patch on the chest could be indicative of a bacterial infection, that infected the internal organs too.
Increase aeration, add 1 TBS salt per 5 gallons to your tank, add Melafix, and feed an oral antibiotic fish food for about a week to 10 days, as a preventative to your other fish.