Hello)

Is that tree allowed to grow outside at all? Is it inside> Under lights? How do you know when to water? What kind of mix are you using?

It's been inside since I bought it, set between a south and east facing window. It's in "Miracle Grow Cactus, Palm, and Citrus Soil". I water it based on a time schedule as for the first couple months I had it, every 8 days is when the soil was dry 2 inches down. It used to be in a miniature pot, the one it's in looks small for it, but I don't see any roots growing out the bottom. I fertilize it every 2.5 months. I have a small lamp in the opposite corner of the room that doesn't produce much light and is rarely on, other than that, there are no lights in the room. Thanks for the replies, I've grown really fond of this tree and would rather not have it die.

I see a heating radiator in the background. A great number of leaves dropping can indicate a great fluctuation in temperature or stressful VPD, causing the leaves falling off a citrus tree to continue to drop until the tree can handle the temperature once more. For starters what is the RH and air temperature of the room?

Yellowing foliage usually indicates either a lack of fertilizer or overwatering. If your not sure when to water you can buy a Large sustee aqua-meter on amazon which makes watering super simple. I prefer the white meters as white is a nice contrast to the blue indicator. Also a xiaomi 4 in 1 smart monitor plant meter gives you realtime sunlight, moisture, temperature, and soil fertility.

The air temperature sits around 70 degrees and rarely fluctuates. As far as I know the radiator in the room doesn't function. I'm not entirely sure of the humidity, but it's 50% 1 floor down. I have a key lime, olive, and satsuma tree in the same general area which are all doing well if that helps at all when it comes to environmental factors. Thanks for the help.