They probably done need to be fed every day because they get some of the extra food that your fish don't catch. Excess food means excess waste which could lead to water quality issues like ammonia build up. But if you have enough filtration, it is okay to feed them a small amount every day, as long as they are eating it. However, since we are still not really sure what's going on with your tank I would probably limit the starfish feedings.
That's definitely a lot of fish to add at once, especially if the tank is still new. There are a lot of things that could have led to the fish deaths. I'm not sure if your lfs warned you against this but I would definitely consider looking for a different store, and definitely consider adding fish more slowly next time.
TyMy first thought is going to be ammonia spike from adding too many fish at once. As the others have said, be sure to add fish slowly to a new tank. It's best to add fish slowly regardless of how old the tank is though. Anemones are going to be difficult and should be saved for an older, more stable tank and until you have a bit more experience under your belt. It's a hard lesson to learn and most of us have been there, including me.
Try this. Wait a week or so and if your parameters stay stable (ex. Ammonia and nitrite stay at zero) then you can add one more fish. Repeat weekly or every other week until the tank is full and you are happy
Remember, nothing good in this hobby happens fast. If it happened fast, it hurt your wallet and made you cry.
