Quote:
You have not murdered your chicks. Ddawn is correct that earthworms are an intermediate host to certain worms that can infect chicks, so it is a good idea to research the topic and know what to look for. It's knowledge you should have anyway. Google can be your friend or use the search feature on this site. I have not fed my chicks in the brooder any earthworms for this reason but many people do and don't have any serious problems.
When a chick is raised in it's natural environment by mama, it eats all kinds of living and dead matter, including grit. Different things can be hosts to different parasites or diseases. Your chickens will be exposed to them all someday if they get outside at all.
When we raise our chicks in the brooder, they do not live in a natural environment. They are contained so their poop can build up to dangerous levels if we don't manage it for them. They eat a manufactured blend of food instead of living and dead matter unless we give it to them. They don't have a mama to keep them warm so we supply heat lamps. It seems difficult to keep them healthy since we don't instinctively know what to do for them but they are pretty tough and normally do fine if we come close to giving them their necessities.
I firmly believe in supplying grit to them before giving any food other than the manufactured starter or starter/grower. Their system is set up for their gizzard to grind up their food for them so they can properly digest it and pass it through the rest of their system. I think grit reduces the chance of constipation or the runs if they eat anything other than the manufactured starter. They have not had a case of pasty butt since I started supplying them grit at day 3, but that may just be coincidence. I give them sand from a sand pile in what will be their run. There are no earthworms in it that I can see. I realize they could still get some parasite or disease from this, but I observe them carefully three times a day for problems. They are going to be eating this some day anyway.
Good luck!