I believe the one that laid then stopped is feeling stress, possibly being over mated as the only hen you currently have that is of age. Cocks are sexually mature earlier than the hens. The others that were 'quite small' were possibly from a following batch... which would put them close to 2 1/2 to 3 weeks behind the others (assuming only one incubator and a non-staggered hatch from your source).
Do you have a second cage that you could move the cock into for a week or two? I'm not suggesting this as a permanent fix, more as a way to let the little ones 'catch up' and the stressed hen to catch her breath. This separation time would also allow your cock to settle his hormones down a peg or two. Seems like they hit sexual maturity and go crazy for awhile.
Once your hens have started laying eggs, would be an excellent time to reintroduce him (unless you discover that some of those little ones are ALSO cocks).
If that is the case, you may need to determine how you wish to deal with that issue. More cages? Re home the excess cocks? Make room in the freezer?