Did a coolant flush recently and filled up reservoir to the full line and filled radiator to the top. Checked out my coolant reservoir couple weeks later and noticed it went down to the low line so I topped it off(I’m using engine ice). Just check it out again today after going out on it once or twice in the days prior and noticed it was once again, down to the low line. Checked the plug and no leaks….anyone know wtf going on ???