I used a 6 person tent car camping with my family this weekend (4 years old and used a handful of times, stored inside, dry, next to all my other gear (which includes 4 other tents all a decade old or older), etc

After first night we noticed a odd smell, like sulfur. we sniffed around, etc and couldn't pin point it. The second night we felt it was limited to one corner of the tent.

after coming home and setting it up in the yard for 3 days with multiple washes/etc, it has only gotten worse (so bad i couldn't leave in an eclosed area as it smelt of sulfur). I was able to pinpoint it to the tent itself, all but the bathtub bottom of the tent (ie the upper part and mesh had the smell...the bag, poles,bathtub/bottom portion of the tent or fly didn't give off any odor.

anyone else have this experience? I have my hunches on what is going on but i am no chemist...

It could be the tent is deteriorating the waterproof material on the tent itself that’s causing the smell.
This next tip works very good for getting smells out of camping gear like tents, tarps or packs. Buy a gallon of white vinegar, dump it in your bathtub with the tent. You can add a few gallons on water to cover the tent with the mix. Let it soak overnight in the vinegar, stur it up a few times to make sure all gets the vinegar mix, set it up in the backyard and spray with a water hose to flush the vinegar off, do a good job of washing it off. Then let it air dry in the sun. The way it works is the vinegar breaks down any organic stains that cause the tent to stink. There also is tent detergents that they sell. I have only used mild dish soap or Woolite soap to wash tents if dirty. Be sure to get all the soap off the tent.

Does it have aluminum poles? They can get an ammonia smell to them. It's possible...

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Yes it did, and i noticed smell in the pole sleeves (but i pulled each pole out of the sleeve and niffed along the length of the poles and nothing from the pole itself)....it was weird, but thanks for the input on the poles.

What did the occupants of the tent have to eat the night before? Wait never mind you mentioned the tub/floor isn't the issue, that heavy of air would certainly sink and impact mostly the floor.

Any sort of visual breakdown of the material? Staining?

the material seemed fine, wasn't sticky or anything like that (and it was a well respected company that made the tent and was used literally 7 nights in 4 years (it is a large 6 person tent), stored inside in conditioned finished basement....i asked the company to send it to their corporate industrial hygentist to see if they can pinpoint what was going on....it was crazy strong smell

my thought was either a coating was breaking down (water proofing, or more than likely fire retardant coating) or the tent itself.

new tent arriving today (i did not go with the same tent, decided to try Big Agnes 6 person this round)

I had some really funky smells with camping gear over the years but nothing like you're talking about.
Back in the day I had a tarp that had a musty smell that was bad when it got wet. when we got back from a week long trip we offered it up to the camping gods in a bonfire