Hello and welcome. You may have two different issues going on here. I don't have any problem, at least that I am aware of with spider mites so I can't offer much in the way of advice. I did a quick search of the entire site for "spider mites" and found a suggestion. Put a piece of white paper on the soil of the tree and give it a shake. Look for very small reddish insects. If you have a hand lens use that to get a look at them.
As far as the other ones, since you only have a few you may just be able to pick them off by hand. Always start with the least toxic approach first, only increasing as needed to remove the problem.
Chinese Elms can be very sensitive to sprays to approach anything like that very carefully. Let us know what you find out. By the way you can use the search function as well to learn more on not only spider mites but other subjects as well. Good luck.