The Cornish cross would be almost twice the size as other standard chicks at that age with as much feathering that has come in. I agree with the leghorn.
I’ve had this little bantam hen for about a year. She has just hatched some chicks today. Can anybody tell me what breed she is? The dad to the chicks is a partridge silkie.
Check the heat lamp you have and make sure it's not teflon coated. It can make birds sick and die from toxicity. Also it could be they are just getting too hot. What is the temp in the brooder?
The first chicken looks more like an Easter egger to me since it doesn't have yellow legs and the color pattern is wrong. Both look like pullets to me.