All dried herbs? (No fresh basil, etc.)

How does each individual ingredient smell?

Guessing, I would say the garlic salt is bad but I would just cook a small portion in some oil, a quarter size, and see what it tastes like.

Never EVER have I had garlic go "bad"....and smell bad...old garlic salt may clump but doesn't smell bad.
I am guessing the OP is unfamiliar with thyme and it's "grassy" smell. It's fine....but maybe you might like another blend for your chicken better.

I like to mix up a teaspoon of garlic powder ( not garlic salt) a teaspoon of salt, 2 teaspoons of paprika and 1/4 tsp ground cumin, half teaspoon black pepper and about a tablespoon of dry parsley flakes....crushed in your hand before adding.
mix and put some in your flour mix for breading chicken or fish or pork chops.

Dried herbs or spices seldom go bad......unless they get moisture into the jars. Even old stuff is typically usable. It just loses the intensity of flavor it once had. I typically aways purchase these in bulk, as I can buy as little as I need or will use in a reasonable time frame.

Scent is such a subjective sense. What may smell "off" to one may have no discernible unpleasant aroma to someone else. If the individual spices/herbs smell as they should then maybe it is just the combination together that is creating an odd aroma.

Many spice combinations can have a 'barnyard' earthy aroma.

Spices don't usually go bad, just loose their potency/flavor. I agree it could be the thyme but give each one a sniff. Mustard and garlic with the grassy herbs could be causing the 'barnyard'.

Making my brown bread today and it has a specific aroma while resting before baking...unusual 'barnyard' scent but I've learned to love it, lol. Rich and earthy. Goes away after baking.

Like mentioned, you should take a bit of batter and fry it.

Perhaps the dried mustard could be funky? Think about boiled cabbage/broccoli/brussels sprouts, which are all in the mustard family and can certainly give off an unpleasant odor.

Get someone else to sniff it. Sometimes my sniffer just goes off. Esp. if you have had a recent cold or sinus infection. Or it might just be that particular combination of herbs & spices smells bad when mixed together. Doesn't mean that it will taste bad--thinking cooked cabbage as a 'for instance.'

I noticed that there is almost a quarter cup of salt for two cups of flour. (1 T. celery salt, 2 T. garlic salt, 2/3T. plain salt) If I was making it, I would substitute garlic powder for the garlic salt and probably leave out the 2/3 T. of salt. As is, it may be approx. as salty as KFC (which I find way too salty.)

I had a neighbor, who doesn't really cook at all ( but she tries, bless her heart!) bring over a container of thyme she had just bought for a recipe she was following. I told her to keep it she might find another use for it like in a turkey stuffing or on some fish. She said..."Eww! No! It smalls so bad!"
So to some thyme must smell bad.

I've had dried garlic turn rancid.

I think the scent of thyme, dried or otherwise, is divine! It is probably my favorite seasoning. But then, other than basil, I can't think of many herbal aromas I don't care for.

My spouse hates thyme and thinks it smells like manure.

Sometimes dried basil smells funky to me.

Thanks all. I think it was the dried herbs that were causing the 'issue'. My wife said it wasn't that bad. I ended up using it and it was just fine (though not my favorite mix and I won't use it again anyway).

Smelling bad may not taste bad.

Have you been to a cheese shop?

dcarch