OP, I wouldn't run tubes, especially on gravel. But as others have mentioned, it sounds like they didn't do a very good job taping the rims, or maybe didn't put enough sealant in. I've retaped two wheels that a shop did, and they're holding air better now, altho tubeless tires will always lose air, just the nature of the beast. But tubeless on gravel is def the way to go.
