stading water in bathtube drains

[not very handy]

I live in a mobile home using a septic tank. We have lived here 15 yrs but never used the tubs, we're shower people.
My two bathtubs are the lowest drains in the house. We only use the shower in the master bedroom which is free standing & has a different drain. I can see standing water maybe 4" down the drain of both tubs but because of the style of drain cover I can't see if there is standing water in the shower also. The shower does drain very slowly but the tubs drain quickly.
The drains aren't big enough to use my snake.
I plan on going under the trailer to maybe disconnect a portion of pipe to check for blockage although I don't think it's a blockage because water drains out of the tub & toilets quickly.
My mother in laws doctor was wondering if maybe mold is causing her breathing problem & coughing. There is no indication of mold anywhere in the house.
Is there a fix for this issue?

[akaothermick]

The drains have P traps that have standing water as a seal to prevent sewer gas from coming up and entering the residence, is this what you are observing? all drain fixtures use this type of P trap sealing. Just like the toilet uses a built in P trap in its ceramic body, the water in the bowl. As this is designed in, there is no fix needed, and as they drain normally, no need to snake them as they are not plugged. In rarely used fixtures sometimes the P trap dries out and the stinky sewer gas comes up the drain, so every week or so, turn on a faucet and add a little water. There are test kits available at most home stores for testing for mold in a home.

[not very handy]

The drains have P traps that have standing water as a seal to prevent sewer gas from coming up and entering the residence, is this what you are observing? all drain fixtures use this type of P trap sealing. Just like the toilet uses a built in P trap in its ceramic body, the water in the bowl. As this is designed in, there is no fix needed, and as they drain normally, no need to snake them as they are not plugged. In rarely used fixtures sometimes the P trap dries out and the stinky sewer gas comes up the drain, so every week or so, turn on a faucet and add a little water. There are test kits available at most home stores for testing for mold in a home.

I didn't know about the P traps or the mold kit, 1st time homeowner can you tell? We're not smelling any foul sewer gas odor, I guess thats not the problem. Thanks for your help akaothermick I'll be going to Lowes in the a.m. for the mold kit.

[pushkins]

You should be able to unscrew two little screws in the shower drain cover and use your snake to clean the blockage out from in the shower. Usually the shower starts to slow down from an accumulation of hair. This would save you a trip in the crawl space.

[not very handy]

You should be able to unscrew two little screws in the shower drain cover and use your snake to clean the blockage out from in the shower. Usually the shower starts to slow down from an accumulation of hair. This would save you a trip in the crawl space.

It appears my shower drain cover was placed without screws, maybe Gorilla glue, Super glue? I think am going to pry the cover off & take a look. Thanks for the info.