Your stool color can change from day-to-day, but unless it goes to almost a white color or to a black, tarry color - or unless you're experiencing very loose stools or diarrhea - I'd suggest you just monitor yourself. You didn't mention having any pain or discomfort, so at this point, there may be nothing to worry about.
The presence of a 'kind of yellowish' stool can indicate you're putting out less bile into your system (the brown color comes from the digestion of the bile that's used to emulsify fats) and that may not be a problem.
But if you experience pain, discomfort, diarrhea, loose stools, nausea or other problems, you may want to consult with your doc.
This is just a guess, but read about you gall bladder and your bile duct.
Make it easy.
Google clay colored stools.