New HBSS
I decided to find another supplier for HBSS and found one: CellGro. CellGro HBSS had the same components as Gibco HBSS, although a couple of the concentrations were different. I tested out this new HBSS vs. homemade HBSS.
Here, the commercial versions of HBSS caused discoloration within a day, but my homemade HBSS didn’t. The high 3.7 mg/mL NaHCO3 concentration (same as DMEM) also caused discoloration by itself. This result might point to me, or our lab chemicals, as the problem. However, all of the components by themselves have never caused discoloration, so they’re likely not contaminated. I’ve also made HBSS from scratch two different times, so I don’t think it’s a mistake on my end.