A while ago, I got a set to grow bonsai trees from seeds.

I managed to grow two tamarind trees from it. One of them is doing very well, but the other one has started to develop some issues over the last weeks. The leaves at the bottom are grey-ish, almost spotted. It only affects the top surface of the leaves (the bottom looks normal) and I can't wipe it off.

The tree has grown new leaves and they look normal, but I'm afraid it's going to spread there as well.

I have examined the tree with a magnifying glass but I couldn't find any pests. Did I miss them? Could it be something else?

Thank you so much for your help!

Could be mites, sucking on the leaves, leaving dead cells as result.
Can you make a close up, of use a magnifier to check out the spots i circled.
There small maybe 0,2 to 0,5mm.

Thank you so much!

I looked at these white spots with a magnifying glass and they are very tiny. It's a bit difficult to say but they could be mites, so I decided to treat the plant. We have very low humidity in our apartment and had a problems with mites before, so that might fit.

Let's hope this solves the problem.

Thank you so much for your help!