Well, for one thing, your water is too cold for betta to live. Temps
in a betta tank need to be 76-82 degrees all the time. If you keep
them in cold water, as you appear to be doing, they will be prone to
disease and a much shorter life. Raising the temperature too quickly
will stress them out as well, so please don't do the
dumping-in-hot-water-all-at-once thing again, OK? If you keep them
warmer, you may find that their health problems improve. Good luck!
dragon