1st it's possible it died from the anemone but I think if it was from the anemone it would've died quicker.
2nd coral banded shrimp are quite aggressive but will more likely kill other cuc than your fish,however they will charge at fish sometimes.
3rd I have nassarius snails, blue leg hermit crabs, shrimp,sea urchins, cerith snails, and turbo snails in my aquarium. Star fish are good but they grow big so they're recommended for a 50+ gallon aquarium.
4th peppermint shrimp,fire shrimp, and pacific or skunk cleaner shrimp are best in my opinion. They all have their own strengths and weaknesses.