Yeah 1% HF solution probably wouldn't ruin a ruby rod or even a quartz lamp but I'd try a mild soap solution and see how that fairs. I'd test a spot with a swab and use lots of light to inspect. It may be a film on there that you are just not seeing. Always start with a mild solvent then go wild if needed. In the future, you can rent a small N2 tank and regulator from your local Airgas for cheap. You should consider that over CO2 because those small crackers can inject liquid which would not be good due to thermal shock or condensation.

Also, thank you VERY much for those holograms! They are AWESOME!