No worries Trevor. Marc helped to point to me specifically where. I was using Steven Miller's processing workflow (Recommend checking out!! It works out well if applied correctly. You can find it here:
https://youtu.be/43ZRVvtK5GI?t=1766).
So using the ColorMask, I generated the Cyan, Green and Yellow mask. You can see that in the Cyan and Yellow mask, is where that hard transition was occurring in my previous pix.
So Marc's comment made me revisit the masks to see if it needed more blurring (but that affected the rest of the mask too, not just that portion of transition). But then I noticed the Green mask provides the smoother transition. So in the revised one I boosted with the Green mask to help the smooth out the transition. But the result is a less blue, and maybe a slight more tinge of green.
However I think it worked out reasonably well. Will need to see if there's any hues I need to tweak further.