Yep.....happened to our 2019. Brought to dealer and they found the A/C unit leaked (I assume it was the lubricant) and it stained the roof. Cedar Creek replaced the A/C unit but there was no concern for the roof membrane. So I simply cleaned the roof area and treated it with a roof treatment calling it a day.
This may not be a leak in the A/C. Could just be the condensation running from the unit. It can stain the roof.
2019 Cedar Creek Silverback 37MBH
TV: 2017 Ford F350 CC DRW King Ranch