I have noticed this white powder on my pothos leaves. Almost like water spots, but comes back after wiping them. Is it some sort of pest?

Is it in a humid area with low air flow? Powdery Mildew is tough to get rid of and very easy to spread. You can try diluted hydrogen peroxide spray, neem oil, fungicide, etc but getting rid of Powdery Mildew is an uphill battle.