Yellowing leaves is almost always a tell tale sign of overwatering.

Yet I picture would definitely help. And of the soil/pot it's kept in.

Soil is always one of the likely culprits in these situations. These plants grow semi-epiphytically so their roots are mainly in organic matter, rather than in soil, which even after heavy rain doesn't stay wet for long. A very fast draining soil is best for them.

Strong light isn't an issue, unless you you move the plant suddenly from low to strong light without an adjustment period. I grow these outdoors and they spend a fair time in direct sun. But one of the differences you have is that indoors there's usually no air movement whereas outdoors there's plenty of air movement even on windless days. In low light situations a lot of the older leaves lower down on the plant will yellow and be shed.

Also, in a dry environment you can get a lot of mineral salt build up in the soil if it not flushed out regularly.

Thanks for all your comments and sorry that I didn't post pics yesterday. I'll post some below, since my phone is having trouble attaching them now.

It is possible that the soil is not right for this plant - what would you recommend that provides the right nutrients but drains well enough?

Given that soil, how often would you water it? And how often/with what fertilizer do you feed it?

as for the possibility of mineral salt build up, I use only reverse osmosis filtered water to water my plants, as the tap water where I live is very hard.

Thanks again for the help!

An epiphytic orchid mix would be suitable. They don't need a lot of fertiliser but you could mix in some slow release. Water to keep the soil just moist and not wet. I don't think giving it a specific amount of water at a specific time interval is the best way to go about watering. Better to do it whenever the plant needs it.

Thanks for your help, tropicbreesent. I will repot it with an orchid mix and try just keeping the soil slightly moist, rather than watering deeply and letting it dry completely between waterings. Hopefully this does the trick! (And do you think it is worth it to keep a pebble tray beneath for added humidity in the air?)

If anyone else has thoughts, I'd welcome them too! (Including about where I could buy another of these plants!)

Thanks again!

Also check to make sure the moisture gets to the bottom of the pot. It's a fine balancing act, you don't want to go to the other extreme and have the top bit of soil moist while lower down is still completely dried out. A pebble tray wouldn't hurt, but you'll be getting evaporation from the top layer of moist soil anyway.

The distance between distal nodes is HUGE. That tells me the plant is not getting nearly enough light

I would also like a source for this kind of plant. I bought some cuttings on eBay a couple of years ago but none of them survived. I saw one at the local nursery last month and it was as yellow around the edges as the OP's plant and was still $40.

Any ideas on where to find a healthy one?

Depends on where you are.

These really like to turn yellow - even at the NY botanical garden, where they get to grow epiphytically under pretty ideal conditions in the rainforest portion of the conservatory, I saw some yellow-edged (but footlong!) leaves.

What should I do with my adansonii? Leaves turning yellow, is it because of overwatering?