Most birds drastically change their patterns as they get older. Like the coloration of partridge in wyandottes and cochins. As adolescents they have barred feathers but as they mature they get their penciling in their feathers instead.
Does his beard look like the picture below? If so I think it is normal. I have seen it on many Millie's but I'm not very knowledgable about the standard besides the feet and the type.
http://static2.mypetchicken.com/images/ChickenPix/medium/Studio_BrdBelDUccle_482_M.jpg