Plumbing question...rancid/sewer-type smell coming from tub and shower drains?

Hello Yahoo! Our home was built in 2000 and we are starting to get a rancid/sewer-type smell coming from tub and shower drains. The smell is most notable on one side of the house where we have a jack and jill bath, but we've just also started smelling it in the master bath shower drain on the opposite side of... show more Hello Yahoo! Our home was built in 2000 and we are starting to get a rancid/sewer-type smell coming from tub and shower drains. The smell is most notable on one side of the house where we have a jack and jill bath, but we've just also started smelling it in the master bath shower drain on the opposite side of the house. The smell seems to be worse after the kids have showered. The toilet seals are good and there is no bubbling in the toilets or drains. Any suggestions are greatly appreciated!!! Thanks much, Billy, San Antonio
Update: Additionally, I've checked the vent pipes on the roof and they all appear to be clear. I haven't blown them out or run water down them yet, though.
Update 2: Hi FOBBG! Thanks for the reply, and my system is connected to the sewer line.
Update 3: Dave, XTX, much thanks as well. Since it's not a septic, I guess one of my options is to have the cleanout checked and snaked. I will definitely have the vents cleaned out as well, and I've heard that using some kind of septic bacteria additive might help too--I guess I could pour that down the drains?
Update 4: Additionally, I'm wondering why I'm starting to get it in another totally different part of the house? Could something be causing a problem with the main vent stack or could the gases be traveling from one part of the house to another through the lines?
Update 5: Amber, Scrunch, RedNek, Mark, and all prior, Thanks so much for your answers and advice! I'll try the easy, passive solutions first (i.e. baking soda, filling tub with hot water, etc) and then attack aggressively if those don't solve the problem. I really appreciate all your time and advice, and I will... show more Amber, Scrunch, RedNek, Mark, and all prior,
Thanks so much for your answers and advice! I'll try the easy, passive solutions first (i.e. baking soda, filling tub with hot water, etc) and then attack aggressively if those don't solve the problem. I really appreciate all your time and advice, and I will absolutely get back to you with the results. I'm currently unable to tackle the problem 'til Tuesday, but I'll get to crackin' on it immediately then.
8 answers 8