Welcome to FishLore! It's great to have you with us! Please read the FishLore Articles for Beginners in the link in my signature. This will help you understand the nitrogen cycle.
Your fish died because they produced too much ammonia in an environment which does not eliminate the ammonia as it is produced. Fish bowls are bad for any fish, even bettas. Not knowing what the pink fish were, you probably needed at least a 10 gallon tank for those fish, with a filter running and a heater. Sorry for your fish.