There are now 3 yellow leaves at the top, if it spreads to the healthier leaves, what do I do? What would it indicate? Do I remove the leaves? Thanks!

The yellowing leaves will wither on their own as the plant sucks all remaining nutrients out of the leaves. It is not necessary to remove them, but you can if they really bother you.

The leaves are likely yellowing as a result of over-watering. Most commercial potting mixes are overly water retentive. How do you decide it's time to water? How do you water when you do?

Good watering practice is to insert a wooden dowel or bamboo chopstick all the way to the bottom of the soil - checking the soil with your finger only evaluates the top inch, the bottom soil could still be quite soggy, therefore suffocating the roots. If the dowel comes out wet with soil clinging to it, the soil is still wet and it is not time to water. Check every few days until the dowel comes out clean and dry. Then water thoroughly so that water flows freely out of the drainage holes in the bottom. Don't water again until your dowel is reading dry again. Good luck!

you can remove fully yellow leaves.

you'll need to pull it out of the pot to look at the roots. if it's cool and damp most of the time (winter conditions) this can rot the roots and yellow the leaves.

what are your temps by the window where it sits day and nite? if it is anywhere close to 65F - it's borderline winter for it and it needs to be watered less as it almost stops absorbing water and goes semi-dormant.

try to keep it someplace 68F at the minimum, 70F is better.

if it's also kinda wilting it means it can't take enough water from the roots - mostly likely due to over-watering. but can also be if it's too dry or too cold. you can't tell unless you look at the state of roots.

you can take a 6" tip cutting with 3-4 leaf nodes and put it in water to root if the plant is very small and you are afraid of loosing it.

The temperature in my dorm has been fluctuating a lot as I live with other suitemate that prefer colder. I’ve been turning the heat on to maintain a stable warm temperature, but it’s difficult to keep. I’ll check the roots and see what’s going on, I think I may have underwatered as I was gone for a short period of time and forgot to water when I got back.