kumquat dropping leaves
My kumquat has been slowly defoliating from the bottom up. It's probably lost over 30 leaves by now. They are just falling off, still green; I've checked a couple times by gently pushing on the petioles, and the lowest couple leaves on many branches will fall off. I've seen this attributed to roots being too cold, but that seems unlikely in this case: I bring my plants inside when it freezes and kumquats are a bit cold-hardier than other citrus.
If anything, it seems to drop more leaves when it's inside. This suggests that it doesn't like it inside, possibly because it's not as humid as outside. I've suspected this and have tried misting the leaves, but it's messy with my current setup. I also have two lemons and an orange, and they don't mind it inside a bit. The kumquat and one of the lemons were recently transplanted into gritty mix, but the lemon (Meyer) got the rougher treatment, complete with some root pruning, and it's happy as can be. What gives?