Reduce the stars size

[Duende]

Hi, I think this is the right place to post.

I have this image and I want to reduce the size of the stars, but without the small ones disappearing. I mean, there are stars that are very big and those are the ones that I want to be smaller.

I have been trying several things and the only solution left is to go star by star manually, but before doing that maybe someone knows how to achieve this in a faster way than doing it manually.

Thanks a lot, I hope you can help me.