Barred rocks and cuckoo maran are completely different breeds.Strange patterned barred rocks are usually known as cucko marans ... also I would agree they could have been over-mated and molting really bad or even had a case of mites. I had a few rescue barred rocks last year and they were molting bad too:
Eggs from BR
Eggs from cuckoo marans
Another difference is leg color
cuckoo maran have more of a pale pinkish color, where as BR have yellow with black wash
Marans:
Barred rock: