Light spots, leaf drop and ill health on chinese elm

TL;DR chinese elms get weird spots and languish, please help!

This fall, I bought a couple of those terrible chinese elms (actual ulmus parvifolia, the best I can tell). I mostly want them as mother plants for an endless supply of CE:s, so I really don’t mind the terrible curves in the trunk. They currently live in my livingroom awaiting spring. A few weeks after I got them they started showing these light spots. I found some very small insects on the bottoms of the leaves, and decided to treat with a surfactant (naturallty protecting the soil). One of them is currently looking good-ish, even if the current sparse crop of leaves are very small (half to quarter normal size). The other one is the issue, though. It looked good for a few weeks, and even got noticeably stronger. And then, the spots returned - only this time with no insects. Fresh shoots shrivel and abort, established leaves get spotted and then shed. What is this? What can I do?

The backlight is there to show the spots clearly. They are barely noticeable otherwise, just slightly “transparent”/less opaque

Looks like bug bites mate. Keeping trees inside, yikkes. Leaf drop can happen when you RH humidity is low, which is often the case indoors.

You already have leaf?? If they are in leaf why not have them outside? Looks to me like the way youre running it, that youre depleting the trees energy

It does, yeah, but I would expect to see actual bugs if that were the case.

The trees are inside because I got them with winter incoming (CE is really not very common where I am in the world), and it is currently inside because they would die otherwise. To my knowledge, chinese elm does not tolerate the kind of temperatures we’re currently having in sweden. Waiting for spring, for sure, but we still have nights of -6 C.

I’ve got such a box store Chinese Elm too. The first year, I kept it inside my apartment during winter and the tree looked very poorly. I had problems with bugs, it lost about half its leaves and didn’t seem to be doing well at all.
After moving the tree outdoors in spring it recovered quickly. I kept it outdoors from spring until late fall and until the leaves had turned brown and fell off. Then I overwintered the tree in an unheated stairwell at a large window. In January, the first new leaves emerged and it has been growing like crazy since then. I had to prune it once already and it’s looking really healthy.
In the stairwell, the temperature was somewhere between 0 during cold winter nights and maybe 10 to 12 degrees C during sunny winter days.

So I wouldn’t worry too much… move your trees outdoors as soon as temperatures allow it and then treat them like deciduous trees, but with some protection / cold storage during the coldest months of winter.