If the hotel has rugs they will be even worse. This is not entirely a result of sloppy cleaning, it is the reality of the humid tropics. Thick towels simply never dry out properly, so they smell of mold no matter how recently they were washed. Part of the problem is the new USA toilet which does not have enough water to flush, but usually the problem is traditional Latin American plumbing. Only solution is abstince or a plumer's friend tool to force reality down the drain.
Brown stains are common in toilets.
In some cases, however, the stain is from minerals in the water, and hence not fecal material or urine stain. So be forgiving if in a geological area of high mineral content. We noticed considerable construction in Belize, especially on the cayes. Buzzing of mosquitos is another nocturnal sound that can cause vacation stress but that is another whole aspect of reality of the tropics. I have organized and led tours throughout the Maya and Andean areas.