I'm sorry for your losses but if you'd like help from people on here you'll probably need to give more information than what you have? How have the fish been acting prior to their expirations? What's the condition of the fish remaining? What are your water params? How old is the tank? How large/what kind of filter/list all inhabitants. Just some suggestions for information you might want to try giving people on here if you're relying on an answer from someone here. Good luck with the rest of them, again I'm sorry for the losses of the others.