When was she last wormed? Are the sores on her midline, or scattered around her belly?
Is she turned out? 24/7 or half day?
If they're right along her midline, they are likely from gnats or no see ums, and the best thing you can do is cover them with Swat, keep fly spray on her and keep her up during the day.
If they're not just on her midline, posting a pic would really help.