Performed system PM on both units. Office materials added 4lbs 410a #326 Checked electrical components, filters, cleared and flushed drain lines, refrigerant levels, and temperatures. The upstairs Rheem unit was low on refrigerant. Adjusted levels to factory range and performed a leak search. Did not get any hits, we will need to continue monitoring levels on the next visit. Possible we will need to perform a more in depth leak search. Upstairs nest thermostat gave a wire error twice in the last month. This could be starting to fail. Estimate added for replacement nest. It also may have been a drain clogg that triggered it to stop working.