If you are talking about digital RA-4 prints and not inkjets, remember that they use the same or same kind of paper and same chemistry and thus suffer from exactly the same problem. You just usually get them with borders cut. If you are seeing a difference in white borders between a digital RA-4 print and analog RA-4 print, there is some kind of problem in your process... Or, if you use the old-style Supra Endura, it might have a bit higher Dmin than the papers used by digital printers. You can try the same papers they use, or try Fuji CA. I agree it's a little bit more white.
Also, blix can cause yellowish staining in some problem cases. As you are using Kodak chemistry, this probably isn't the issue but check that it's fresh and correctly mixed.