just one advice :) Every time when you buy new betta always quarantine it for a few weeks. It always chance to get sick betta. You actually have to do the same with any plants that you buy. Never share anything between new fish and your other fish. And one more advice the more water changes the better even for big tanks. And always make sure you clean filter media.
Thanks sunlight, I appreciate that. I do have another betta Kudo but he's in a 10 gallon tank and he's doing great. I've had him for almost a year now. I ended up disinfecting the other tank completely and selling it. Not sure exactly what happened with Spyro but I've been closely monitoring Kudo and ensuring it does not happen again.
Hey sorry for your betta:( Do you have another betta? 5 month not really long for betta do you need to figure out what is the problem to begin with so it not happened again? Also make sure you disinfect the tank if you decide to put another betta in that tank. Good luck.