Hi mt,
A few problems potentially here.
First, I thought pea puffers are aggressive and recommended 1 per tank
Also, danios and tetras should be kept in larger size groups
I believe your tank is too small for the needs of a kuhli and that they should also be kept in groups
I'm not familiar with killifish. What kind do you have?
If I were you, I would look to increase the number of tetras and danios, assuming they're the smaller size ones, trade the loach for a group of cories.
I know it's interesting to have a lot of different fish but we are responsible for making sure that we provide them with the best environment for them. Good luck!