Brown spots (generally with some yellow/whitening surrounding them) on a Golden Pothos can be caused by a few things. These seem to be the most common: 1 - Too much fertilizer. Golden Pothos doesn't like much fertilizer. Like, a little bit every 2-4 months is plenty, if at all. 2 - Root rot conditions. These conditions can be fixed (if caught early on) by aerating the soil (chop it up/loosen it to get air to the roots), and letting the Pothos dry out more between waterings. If it's necessary to get better water drainage altogether, you might need to re-pot the plant.