btw temperature was a steady 74 F

A 5 gallon tank is not to small. It might of been the accident of alot of food the first day. Although I reccomend normaly feeding fish 3 times aday,you have to watch how much food you feed at each time that is the key.

Ty for the advise on the food. btw it's a .5 gallon not 5 gallon or inother words 1/2 gallon tank.

Hi
To the above I'd add What did he look like when you bought him?? So many places keep them in small dirty jars and to me it seems a miracle any survive.. He may have been doomed from the getgo.
I'd suggest at least a gallon larger is certainly better. When you get a replacement look at all the fish .
are they active ,good color do they flare at each other.?
Water clean and well maintained??
If part or all above is true buy elswhere. Far easier to maintain a healthy fish them to cure one no matter what species!! Good luck Bettas are VERY hardy fish for sure as proven by how much abuse they endure in so many vendors gary

i think you just feed your betta too much when i got my betta there was a label on the container he was in. it said to only feed the bettas 2-3 times a week. you probably overfed him.