Have you been tested for fat malabsorption? That condition can also result in a foul-smelling stool.
Yellow stools is normally a sing off the stool passing through the Colon to quickly. When the stool starts of it is either yellow or green, and the bile that the liver produces then turns it to its brown tyoe of colour. If it is passing through to quickly, the bile cannot interact with it, therefor causing the colour to remain unchanged.
Also, Malabsorption is another reason for the stool staying yellow. With Melabsorption, the stool will be fatty becuase the colon is not taking the nutrients (fat, carbohydrate, and protein)that is needed from it. Therefore, causing the stool to be fatty and sink to the bottom, or in most cases floot to the top.
With regards to the thinning of the stools, this can be cause by any number of things. First, IBS is a big cause of this. The colon contracts and because of this, the stools do not have the chance to form correctly. Keep a look out for the likes of mucus (a clear looking liquid) when cleaning after a bowel movement.
Speak to your doctor about it in more details, any number of thing can cause it.
I wish you good and steady health my friend.