We have to start with some data. Sounds like things are out of wack here.
Temp and temperature stability
Nitrogen levels (nitrate)
Do you use RO
Obviously add no more live stock. Puffers can be hard to keep in perfect systems.
Take a deep breath and use this experience to learn. Don't just buy live stock that you want, buy live stock that you can keep healthy long term. As you are finding, it can be a true letdown when things don't just work out of the box. We all have been thru this.