I bought several ducklings from a breeder 1 1/2 weeks ago including Cayuga, Pekin & mixed breed. The smallest 2 ducklings (not sure of actual ages & if these may be youngest) had very little sound when trying to chirp and have since lost all sound or “voice”. One seems to be eating fine & is growing like the rest. The other does eat but not as much and has not really gotten any bigger. Should I be concerned? They started in a bin and moved them to a kiddie pool about 4 days ago. They are inside my garage for now due to predators until they get big enough to move to outside coop. Bedding is changed daily or every other day and fresh water 2-3 times a day. Food is store bought crumbles and I recently started giving them lettuce for snack.