[Whippet44]

He's not necessarily dying. I think it may be SBD. That is, Swim bladder disorder. Not disease. Six pellets is a bit much. I think for now, try fasting him and Epsom salt baths. Do small but frequent water changes. Bettas can last a long time without food. If I feed even 3 pellets to one of my bettas, he looks like he's on the verge of exploding

 

[Whippet44]

Absolutely agree, Nick. OP definitely should've done a water change by now. Do ten percent, wait ten minutes, do another, wait ten minutes, and so on until you have done a 100%. This way, your fish won't get as stressed.

 

[Whippet44]

It's very unfortunate that you lost him. A tank below 5g is not worth trying to cycle. It's extremely difficult. You must do a lot of water changes in a tank that small.