Pothos is getting brown spots and dropping a lot of leaves. It has tended to do a leaf drop in the past but not of the duration of this one. The plants are in the same spots that have occupied for at least 5 years, so I don't think it is a light problem.
Pothos Is Getting Brown Spots
Certified GKH Gardening Expert
This could be overwatering or even under watering. The soil should dry out slightly before watering.
I would also inspect the plants for insects.
Neem Oil is a good treatment as it works as both an insecticide and fungicide. It's safe for people and pets.
You also can trim up the plant to clean it up. Repotting and refreshing the soil may be a good idea if this has not been done.
Salts can build up in the soil and cause leaves to turn brown.
Here are some links with more information.