Pothos is a fairly resilient indoor plant, but can be stressed by over-watering and lack of light, even though they are tolerant of lower light levels in general. Ceiling fluorescents are better than nothing if natural window light is not available in its growing space, but they are usually not sufficient by themselves to support good long-term growth and overall plant health because they are dim as far as plant photosynthesis needs are concerned. (Our eyes aren't the best judge of light level with regards to plant needs, since they adjust to low levels pretty easily, so it's hard to make comparisons with brighter conditions.) A grow light may help to supplement its light needs, or moving the plant closer to the fluorescents (if possible). If the plant has been growing satisfactorily well in that light level so far, though, then you can probably keep things as they are. The only consequence in that case might be that the overall plant vigor is reduced, which hampers its ability to regrow well or lushly after damage or leaf removal.

Gradual yellowing and shedding of the oldest foliage is normal for indoor plants and is part of the natural aging process for those older leaves. When it occurs on younger foliage or is more excessive overall, though, it suggests the plant is stressed by growing conditions, a pest outbreak, or a disease. From the photos in this case, it's hard to tell what caused the yellowing/browning spots on the leaves, but it might be a minor infection. We don't see any pests present, though you could check the leaf undersides as that is where most insects would be hiding/feeding. Thrips would be one possibility given the appearance of the damage, though we are not convinced they are involved based on this type of spotting. For now, just clip off the leaves with prominent spots, if there aren't too many of them where removal would denude the plant too much.

Is the plant misted with water or sprayed with any other substance? If misted, which some gardeners do in attempt to boost humidity for houseplants, discontinue that because not only does it not improve humidity enough or for very long, but wetting leaf surfaces can allow disease spores to more easily infect a leaf. Occasional showers in a sink to rinse off accumulated dust on leaves is perfectly fine, but regular leaf misting should be avoided. Sprays with certain pesticides, including home remedy alternatives (using dish soap, rubbing alcohol, etc., which we do not recommend but which abound in online forums), could cause phytotoxicity if a plant is sensitive to the ingredients or is under stress from dry soil, overwatering, or some other issue at the time. (Phytotoxicity is simply plant tissue damage caused by chemical exposure.)

Leaf damage can't heal, so discolored or crispy areas won't go away, but phytotoxicity damage will appear soon after exposure but will not spread and keep creating new symptoms compared to the way a pest outbreak or infection might. For areas with cosmetic damage that aren't threatening plant health (if no pests are visible and it does not appear to be an infection), leaves with few spots don't have to be removed, as the rest of the healthy leaf tissue is still capable of feeding the plant. It will yellow and fall off in its own time in that case as new growth continues on the stem tips.

Pothos grows best when allowed to get somewhat dry between waterings, when the soil is felt around an inch or two deep (how deep depends on pot size). They shouldn't wilt between waterings, but also shouldn't stay constantly damp. If the pot sits on a saucer (or for a hanging basket, has an attached saucer) or inside a decorative cache pot with no drainage, be sure to empty that container after watering so the drained moisture doesn't soak back into the root ball and drown roots. While potentially not directly related to what's going on with the leaf spots, sometimes leaf damage from environmental stress like soil moisture or very warm or cool temperatures can look convincingly like pest or disease damage. Is the plant in the direct path of a heat vent or near a drafty window or cold window glass?

If you find what you suspect are pests but aren't sure, feel free to send us photos for ID. For now, you can either clip these spotted leaves off (at least the yellowing one with more spots; the second leaf with a bit of brown looks better) or leave them alone and monitor the plant for worsening symptoms.

Miri