Falling cause leaf drop?

[lauraeli]

Plant got knocked over (onto the ground, out of the pot) and dropped two leaves. A week later it got knocked over again. I potted it back up and moved it under the grow light. Next day a healthy leaf started to yellow and it is looking like it will drop that one now too.

This one is not healthy. It has only one short root after the two new roots failed to adjust to being buried in the growing medium.

But it has no rot, so why does it continue to decline? Why would it choose to drop a healthy leaf, when it had only two? The leaf was not damaged, nor was it dehydrated.