Hi, I came across this thread while trying to find out what is wrong with my Monstera and was hoping someone would have some advice. The last two photos are of a leaf that I trimmed off the plant. When I first got the plant this leaf had a large brown spot and was yellowing with a few of the black tiny lines. I didn't worry too much because all of the other leaves appeared to be fine. Since then the leaf is now covered in these tiny black specks on both the top and bottom of the leaf. I have now noticed that the underside of the other leaves have also started getting the black spots (the first two photos). They are slightly raised bumps and look like tiny lines. I have googled lots of diseases and signs of not enough/too much light or water or root issues and so on or even possible insect eggs? but I can't seem to find anything that matches up.
I have another two Monstera's that both don't have this problem.
I would greatly appreciate any help. Thank you!
(the Monstera is kept indoors in filtered light but the photos were taken at night)
