Jenny (Gotenburg, Sweden) on 10/05/2012:

It went away when I started to give them cod liver oil.

Your daughter could have a vitamin A or K2 deficiency which becomes worsen when the vitamin D levels gets to high during summer. This since they're often used together. You could try giving her more egg yolks, fish and butter or feed her cod liver oil or other suplement. You can read more about the issue if you google Chris Cresser.
Good luck