Very Yellowing Variegated Pothos
I have a 3 month purchased variegated pothos hanging in moderate to bright light. Over the last 6 weeks, it has yellowed severely, up to 20% of its foliage. My other pothos and all other plants, however, are doing quite well. It is highly variegated, with pale green and white. Watered weekly, very light fertilizer monthly.
I question if the problem is underfertilization, since you say the plant was purchased just 3 months ago; growers generally fertilize their plants sufficiently that no fertilization is necessary for 6 mnths. In fact, if you've been fertilizing steadily, there could be a build up of soluble salt in the soil. The first thing I would investigate in a pothos with a lot of yellowing is the possibility of underwatering. There should still be a bit of moisture in the soil when you water again. In fact, I would set the pothos into the sink and run several quarts of water through it, to wash out salts, in case that is the problem. Then use a wooden dowel or skewer to test the soil moisture between waterings, and if you find it getting too dry, slightly increase the amount of water you give it when you water your other plants. Also carefully examine the leaves and stems for signs of mealy bugs.
If all factors are similar, I would guess the plant might be needing a stronger feeding. If grown under a high fertilizer regimen, your pothos is hungry. Don't over-fertilize, or you may burn the roots. Just follow package directions. If you see signs of improvement, increase feeding to halfway between what the pacckage reccomments and what you've been giving your plant.