I'm not really sure if there is any particular 'age' when they can molt. This is the time of year when molting does start in our flocks so if your's are molting it's nothing to be alarmed about. Case in point: my 4 BA girls were only 3 months old when one day it seemed like the run was filled with feathers....everywhere! I almost had a panic attack!!
They were going through what they call a 'juvenile molt', doesn't happen all that often, but it sure scared the bejeebers out of me at the time...chickens...go figure!!
They go thru partial molts as they go from fluffy down to feathers…first around 8 weeks or so, and several times as they mature. You shouldn't notice any looking naked or like pics of adult molting during that time, but will find the cast off feathers. Then, I guess it depends on time of year they were born, but those born in springtime likely will get their first real molt at 18 months or so. Late summer to fall when days get shorter. After that, I don't know, but hope they will do this ? annually cause the new feathers are clean, soft, and they look young again.