At 6 weeks, I'm thinking pullets. Some of them can be sneaky, so I wouldn't say 100% that they're girls yet, but as you observed with their father, all my boys have been VERY obvious sooner than this. I'm not sure because I have very limited experience with broodies raising chicks, but I doubt that would make a difference in development like that... All of mine have been raised by hand in a brooder, so I don't have anything to compare in that regard.
If it offers any reassurance, here's an assortment of male and female bantam Cochins I've raised, all at 6 weeks in these pictures:
Males:
View attachment 1930873 View attachment 1930874 View attachment 1930875 View attachment 1930879 View attachment 1930880
Females, mostly developmentally similar to yours:
View attachment 1930870 View attachment 1930871 View attachment 1930872 View attachment 1930876 View attachment 1930878
These birds are all much older now, so sex is confirmed on all of them.