Never had a problem with any major discoloration on Argentium ss, nothing a quick pickle then the usual polishing. I use Argentium 960 from G&S metals. I heat just the area to be soldered , flow the solder then remove the heat. I let it air cool for a few seconds then quench. The solder is argentium solder. And no special pickle. I find Zam for a final polish gives it an awsome shine.
It takes a little bit to adjust to it but I love working with Argentium.