Linear Fit can make sense at this stage if your filters are well balanced. With my Astrodon filters that are very close to 1:1:1, I sometimes (often) get better results with it than I do with BN and CC. Learned that trick from Oldwexi (Gerald).
That said, my best guess on Michael's issue from looking at the image is that all of that is beside the point. I have had this happen in the past in my own case, though there it was with green halos on the small stars, due to focus issues. That is likely to happen one of two ways. Either the filters are not parfocal and require separate focusing for each filter or your focus slipped and you were doing each channel separately. Assuming you are doing the typical LRGB sequence, then it is most likely the fact that the filters have different focus points.
A solution would be to image each channel separately and to refocus between each color switch. It sounds like this is a persistent problem and that is worth a try to see if that fixes it. One way to save what you have done so far, at least in part, would be to shrink the offending stars in the stack that is bloated but that can be frustrating.
Hope that helps.
Best,
Jim
