STINK

Roadstar, had the same issue with my Springdale. Finally found that the slide seal had leaked during killer rains and the carpet in the dinette storage area had gotten wet and the plastic bin I had on the carpet didn't let it dry=mildew. Man it stunk.

If I don't add chemicals will detect some odor,you may have residue left high up in tank. Use a spray wand to flush tank unless you have built in sprayer.

Did you have all the windows and doors closed, but a vent fan turned on? without a window cracked the vent fan might be pulling "air" from the bathroom/toilet?

Dumping every 3 days could be contributing to your problem unless you're filling the tank with lots of water just before you dump.

Stink ? Toilet smell or mildew smell? before we all go throwing ideas at the wrong target.

If it were me the first thing I'd be checking is the knobs on your stove to make sure one of those didn't get bumped to the on position.

Ah, come on 3 Dog, you're taking the fun out of it! Logic? we don't need no stinking logic!

Grey tank can smell as bad as black. We add chemicals to our grey tank also. Bad valves under sinks can cause odors from grey tank to come into the RV. If you have a washer dryer that you haven't used in awhile, add some water. The trap dries out.
Also check the batteries. Batteries without water have a terrible smell!
In the summer when temperatures are high, we have to add 2x as much chemicals to the black tank.
Has anyone full timing used the new Dometic chemicals for full timers?? Saw it at Camping World.

Is this the camper in your signature? If so, when did the problem first start? What is different now than before? If it is the same unit, my first thought is you have a buildup in the tank. Second would be the seal at the bottom of the toilet.

Do you use deodorant? I need to when the temps are up. Haven't used it all year till we got to San Antonio. Will probably need it till we get to San Diego.