New to bonsai, need help

Hello I am quite new to bonsai, I can see few yellow leaves, I mistakenly added white vinegar in the soil but immediately washed it and added new soil, is my bonsai dead? Or is it healthy? How to take care of it? Many thanks

This is a chinensis elm. They sjould be outdoors.

Nothing wrong with the plant, shame about the rocks, they look awful and are stopping proper watering and drainage.