Is it normal?

Mine peep softly much of the time. When the peeping gets loud and has kind of a distressed sound, I knew they were unhappy (sometimes too warm or cold, etc.) Mine would also peep loudly if we were holding one - the other 2 would really carry on till the held one was back with them.

 

Try warming up the brooder a little, mine peep more when they are not warm enough.

 

I bet they are looking for the chicks you had to give away. I am sure they will get over it soon.

 

I have a little one that never stops. I swear she "talks" in her sleep as well. She is with my others. Only Audrey leaves the brooder frequently. Temp is perfect, food water etc. But still she peeps away.