I'm very sorry for your losses. You need to secure your coop before getting any new birds or you will lose them too. There are any number of predators that will enter a coop at night, foxes, raccoons, etc. Your coop needs to be secure so the birds are safe. The coop should not be open at night, it should be closed after the birds go in for the night. Even a closed coop, if not properly predator proofed can be gotten into by a determined predator. And the predators will continue to return to where they are successful. I would do some searching and reading on predator proofing your coop. It may take some effort, but it's worth it in the long run. Otherwise you will just be running a predator restaurant. If you want to post pictures of your set up it may help getting suggestions, you can also look through the 'coop and run' and 'predators and pests' forums for ideas and information.