It does sound like the soil does not have a chance to become fully saturated again. I would never try to water a hanging plant in place because I put at least a gallon of water each time, and most of it runs out. Peat seems to be the primary culprit of hydrophobic soils, IME. And silicone moisture crystals, when present. If the idea of taking your plant to your shower/tub to water sounds like too much of a PITA, try giving it a reasonable drink, then repeating an hour later. Add water as slowly as possible. Maybe put a bucket under at first, then the towel. Think of a wet sponge that sheds water at first, then accepts much more. Then realize that if the soil hadn't really been getting moistened before but now is from an altered method and that you are able to much more fully saturate the soil, it will take longer to dry out. Monitoring how heavy a pot is is an excellent gauge of whether or not the soil has dried. But, understandably, not practical for all of them. I recommend it if possible/practical, whether watering in place or in shower/tub.

Probably just some physical damage. Don't snip it off. It's a fully functioning photosynthesising leaf. The plant needs it.

FYI - some nutrients (N, P, K, Mg, et al) can move about inside the plant. Others are considered immobile or nearly so. The immobile nutrients, like Ca, must be available in the soil and in the nutrient stream at all times for normal growth. When there is a deficiency of any mobile nutrient, the plant will rob the nutrient in short supply from other plant parts to provide what's needed for new growth. Normally, the plant robs these nutrients from older foliage, or foliage closer to the stem/trunk in plants with branching structures. After the nutrients are extracted from the sacrifice leaves, they are shed. We don't know if it's light or fertility that's causing your plant's leaf loss, but there is no doubt that 2 years w/o fertilizer virtually insures more than one issue related to nutrition is in play. I'd say a good plan would include A) trying to fix the low light issue, B) get started on a fertilizer regimen that makes use of a high quality soluble synthetic fertilizer (like Foliage-Pro 9-3-6), C) get your watering under control by using a 'tell' to 'tell' you when it's time to water. If the pot the plant is in was plastic, you could easily tell when it needs water by hefting it to test its weight, but that doesn't work as well for clay pots - which ARE the best (conventional) choice, IMO. Using a 'tell' Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support good root health, which is a prerequisite to a healthy plant. Watering in small sips leads to a build-up of dissolved solids (salts) in the soil, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor. In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water. Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'. One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue. You might find this to be helpful. Al

I might try fertilization, but that's not a sign of low fertilization. Pothos just don't care as a general rule and simply stop growing. Ken's right, it might be heat, or other stress, causing it. It doesn't look like overwatering or underwatering. Pothos don't generally suffer from tipping (chlorine, fluorine, or other salts in the water issues), either. Disease is possible, but the rest of the plant looks so amazing it seems unlikely. And even if it were potbound, pothos are unlikely to complain too much about even that. I'd look for stress first. Does the sun hit that at any time (I'm saying no because it really wouldn't care about a wink or two and mine sees far more). Are there pests in the soil? Maybe give it a light feed to see if it helps, but I don't like randomly throwing things at a plant if it's unnecessary and we're not sure...