Any ideas on how old these chicks might be?

[RennieRose]

My DH brought home 3 BO chicks April 6th.

He had purchased them at a local feed store and forgot to ask how old they were until he had gotten home. We've had them for 3 weeks now.

One chick started to get her feathers later than the other two. Below are two pictures of our chicks. Does anyone have an idea of about how old they might be? Thanks in advance for any info.

 

[Aeropennchick]

I think they are about four weeks old now. I have two buff orps from the TSC and they are now seven weeks old, and I took photos every week. I have a good selection in my album, Feathered Kids, which is linked in my signature below, if you want to look!