I had sanded off to the base but could well have missed a spot. Makes sense. @Noyade and @EricL i am hoping to not have to re-strip this back (time frame is tight, as I’m going away in two days) can I add something here and paint over with remaining tub & basin paint? For example Zinsser primer sealer stain killer then paint over? Appreciate any remedy/advice
I'm sorry but Zinsser primer is not compatible with White Knight Tub and Basin. I recommend keeping the coating you have on rather than stripping it back. The product that you've put on is actually an epoxy enamel and provides a very robust showering surface. It is formulated to be used in showers, ordinary primers and paint will just peel off in a matter of days. I'm sorry but the discolouration in your tray is just too strong. I suggest going over the discoloured spots that stand out with extra coats as suggested by the Tub and Tile paint manual. I recommend doing a light sand on the area that was missed so that you can put on a coat in that area as well.
If you need further assistance, please let us know.