Are these enough invertebrates and do they get along? And what do they eat?

[clownfishmama]

For starters I have a 15 gallon tank.
I have 2 blue leg hermit crabs the fighting between them was recently or at least a few days ago one was chasing the other and God they run so fast and then the one chasing it was digging inside the other's shell. Was he trying to kill him? I broke the fight up quickly.
I also have 2 Halloween hermit crabs, they seem to be doing fine no bullying from them. I have 3 scarlet hermit crabs. They don't fight but mostly takes a minute to find them because they're so hidden, though the baby is always out and easy to find. And last but not least I have a Blood Red Fire Shrimp he's always hiding and staying in one spot. What do I feed all of them? Is it too much invertebrates?

 

[TX_REEF]

Doesn't sound like too many inverts. Make sure you have empty shells larger than the current hermit shells available, or they may kill each other for new shells - that aggression you witnessed could be related to that.