Now that i know the split function creates a new list that can't be saved, I found a new way of changing the values.

health_list = healths[ct].split(",")
health_list[cn] = str(int(health_list[cn]) - damage)
healths[ct] = ",".join(health_list)

I need to just make a temporary list as a placeholder then join the list back together with the new value.