Good day everyone:)
The leaves on this pothos are starting to turn yellow. We have already removed a couple of other yellow leaves. We've had it for around 3 months. We re-potted it in a large pot when we bought it (not knowing any better at the time) in a mix of potting soil, Dynamic Lifter and cow manure (yeah, it smelled for a while!). Last week it got a feed of weak liquid fertiliser. It gets watered when the top inch of soil is dry. Those windows are north-west and north-east facing. We live in Australia in a Mediterranean climate, so lots of sunshine in summer. Oh, and we seem to have a few fungus gnats.
If anyone is able to help me understand why the leaves may be yellowing and what I can do to fix it I'd be very grateful.

Yellowing is either a sign of underwatering (but you'd notice wilting if this were the case) or overwatering. Depending on how big the rootball was before you repotted, the current pot may be too deep or big. I don't know what dynamic lifter is or if cow manure causes it to stay more moist, but fungus gnats are a sign of overly wet soil (and usually that's a sign of peat in the soil... some dislike peat, me, I don't have much choice but use potting mix with peat in it).

I think it's likely that the pot is too deep. Plus, I didn't know myself about Dynamic Lifter but I just looked it up, and it does apparently have have moisture retaining properties, in addition to slow release fertiliser. It's advertised as a 'soil improver'. I think in combination that may well be the issue. I'll try and dissuade my other half from watering it for a while! Thank you for your response, very helpful:)

I just re-read my comment and I wanted to clarify that you usually see wilt before yellowing when it's underwatering (I think that could be read as wilting with over or underwatering, although... if overwatered enough, plants will wilt due to root rot, but you'd be able to tell the potting mix was too wet).

You could repot it if you're up to it!

Your Pothos looks very healthy. I see only one yellow leaf. A limited number of yellow leaves is inevitable and not a cause for concern or necessarily doing something different. As long as your Pothos is adding more healthy new leaves than losing older ones, you are generally on the right track.

Pothos are hardy indoor plants because they do not need or even like the direct rays of the sun falling on them. Your "down under" north-facing window will provide too much sun unless you cover it with a sheer or move the Pothos back away from the window and beyond the range of the sun's rays.

Your watering is probably about right, but you may be allowing the soil to get just a bit to dry. On the other hand, you will need to allow the soil to dry as much as possible in order to deprive the gnat larvae of the moisture they require

The wonderfully organic soil that you used is terrific for OUTDOOR plants but not recommended for indoor plants. It is a non-sterile mix that comes loaded with potential pest and disease problems. Hence the odor and the fungus gnats. The gnat larvae feed on any decaying organic matter. Keeping the top layer of soil as dry as possible is the best antidote, but if it gets too dry, you will get more leaf yellowing.

If the original rootball is still intact, then you can consider undoing the repotting you did by removing that soil and manure you added and putting the original rootball back into its original pot without any added soil.

If you removed a good portion of the soil from the original rootball, then trying to replace the soil you added may be very traumatic to the roots. In that case, I would try to wait out the gnats and hope they go away without repotting.

For future reference, use a sterile potting mix that consists only of coir, peat moss, and perlite.

Georgia: Thank you so much for taking the time to clarify, much appreciated:)

Will: what an amazingly helpful post, thank you. I was wondering if it was too sunny a position for the pothos - seems like I can move it to another less sunny spot and free up a place for a sun-loving plant - yay, new plant! There's so much for me to learn from your post about how to look after houseplants. I've done a lot of reading but somehow when the info is directly related to my own experience I learn a lot more - thank you again!

In your zone, Pothos might be happier outside, but possibly invasive. Specimens out in the sun with a tree to climb develop enormous leaves with interesting splits in them.

Pothos (Epipremnum aureum)

Tiffany, I'm not sure if we're allowed to plant pothos outside. We do have a spot that gets next to no sun in winter and a lot of sun in summer where we are looking to grow a creeper...I may look into it. I don't want it escaping from its spot.