Here is a picture [ imgur.com/a/927gP ] of my 1-year-old maple tree. After winter (about 1 month ago), I repotted it and cut some of its roots and have been regularly watering it (not overwatering it hopefully), placed it outside in a half shade but I have been noticing this strong yellow blotches on the leaves that turn into black spots. The new leaves look better but I'm scared of losing my bonsai. Help!

My first two thoughts are too much water, or anthracnose, both of which could be resolved by letting the soil dry some between waterings.

There can be as much danger in letting a tree be soaked as in letting it dry out.