are you sure nobody opened a window on a nice day.. and left it open too late.. causing a cold event???

no plant holds its leave forever.. so some shed is not unusual at season changes ... like when you go from winter sun intensity to summer sun ...

but i cant really tell if thats whats going on here ...

maybe you should try letting it dry a bit more .... perhaps the media is not moving water to drainage.. like it used to ...

whats the dead stick to the left of it.. in what looks like mother earth in a pot ... my point simply put.. it doesnt look like potting media ... and maybe thats why that failed ... what actually caught my eye.. is what looks like worm holes ... whats that all about .. lol .. maybe a new hobby i ought to look into ...

ken

https://duckduckgo.com/?q=worm+holes+in+soil&t=ffcm&iar=images&iax=images&ia=images

Thank you Ken for your thoughts! I’LL try letting it dry out more and see what happens. The soil I mix myself with high quality all purpose, perlite, spagnum, and whatever else (depending on the specific plant and it’s needs). I had hoped the sad looking plant to the left would go unnoticed, LOL. It is a lemon grown from seed that also dropped it leaves (though I know why in this case). It’s top dressed in black sand because of a fungus gnat issue from a while back - I plan to repot and remove the sand this spring. The holes are from the water meter.