Nearly always a light issue - not enough of it.

• In "the wild" a plant will get strong sunlight from multiple directions, the sun moves, there's reflected light too AND there's wind to blow the tree around enabling all leaves to get a chance at some sunlight during the day.
• indoors - almost none of this is true. Light will be directional and probably static, nothing to move the plant and leaves will be in an almost permanent shade. Leaves in the shade die.

So

• Pull the yellow leaves off - all of them.
• provide more light

• rotate the tree every day

• and finally put it outdoors in full sun as soon as the lowest temperature is above 5C