Meiwa kumquats are about the hardest citrus tree to grow. They do things like this. Mine do. Don't know why.

Mines doing this too but the leaves turn yellow first in the middle shaft before falling! I'm not sure why but I heard that when they flower it's a stressful time for them and mine is flowering so maybe it's taking its energy away form leaves to the flowers. Are yours flowering? I hope someone with more experience will chime in!

Hibiscus, I find that Meiwa is a very fussy citrus, little thing and it will start reacting. My Meiwa is a slow growing tree, it was covered in blooms couple months ago and has only one fruit on it right now :(

So frustrating.

My first meiwa actually did the same thing- a rapid onset of leaf drop. Did not recover.

The top branches on this current one have now turned black overnight, so they are gone. I'm down to one branch and a smaller one that has insect damage.

I've had meiwa from 3 different growers, and have had issues with all of them. Of course, being fairly new to citrus, my lack of experience may also factor in.

I have another meiwa that suffered significant root disturbance (critter) last spring. Pleased to note that the plant is currently carrying many fruits, hoping they make it to harvest. The resilience of the plant is encouraging.

The vast majority of Meiwa kumquats trees are on incompatible rootstock and do poorly or die.

Steve