I received my Chinese elm as a present in July! I watered throughly when it needed it and placed it 3ish metres away from a SW facing window - and it flourished throughout our crazy English heatwave! Then the cold came and it started to struggled and rip leaves so I moved it to the windowsill to get more light. It was doing okay then suddenly dropped the majority of its leaves and sometimes there is a little white ‘stuff’/mould on the soil.
This is my first bonsai and although I’ve done a lot of research I just need some advice. Is it okay? Has it went into dormancy? Is a windowsill the best place for a bonsai? What should I do next
Added multiple pictures including one where it lives.