I bought 3 gold sex link/gold comet/ gold star..people use so many different names. anyway I bout 3 at the same time when they were 3 days old. they are now 7 weeks. they are eating 20% chick starter. 2/3 are growing fine. the other is significantly smaller, like almost 1/2 size. I have no idea what going on with her. all are pullet chicks. the runt looks healthy, she runs and flies and jumps fine. she eats and drinks good. she isn't denied food by the other chicks she just isn't growing or is growing significantly slower than the other 2. any recommendation what to feed her so she can catch up?