DD#1 had this - it was also picked up at her 6mth checkup. The health nurse said it was nothing to do with how I had cared for her, and that it was nothing to worry about. She said I could see the GP and get some hormone cream for it, or that I could wait to see if it had corrected itself by her 12mth checkup.
I chose not to do anything, and it fixed itself - and she hasn't had any problems since
The nurse also said that sometimes the hormone cream will fix it - but then it can happen again anyway, so sometimes its better to just let it be.

HTH