OP said that when he turned on the stove and smelled the burners, the odor was different...so this is probably not propane related. To completely eliminate propane, turn the source valve off and blow the rig out, then close it up and see if you still get the smell.
My bet is that if the rig has been sitting for awhile without being used, one or all of your traps dried out. Run some water in each sink and your shower to fill the traps back up. As mentioned, your gray tank will have an odor very similar to propane, depending on what's been in it.
This happens with ours when it's been sitting for awhile unused. Part of our "start up" list is to run water in all sinks/shower.
Jim