Re: brass hookahs (myas) start to get weird smell
Mya stems don't clean well because of the rough brass texture on the inside. Flavors sit in there.
What you should do first is buy a Tangiers flavor. Tangiers is designed to clean out old smells in your hookah. You need to smoke a couple bowls of this.
If you can't smoke tangiers, then let the stem sit in a batch of baking soda and lemon juice. Make sure there is a ton of baking soda inside the stem. It absorbs smells very well.
If the smell is still there, fill the stem with baking soda and let it sit there for a couple days (maybe 3 or 4) and then clean that out and see what happens.
If it still smells, you need a new Mya (seriously).