Senior dog advice

My 15 year old rescue mutt has severely slowed down over the past couple of months. His right lip now droops and he drools, he doesn’t eat much (never was very food motivated to begin with), is panting almost the entire time he is awake and has an infection in his eye that meds won’t kick.

His most recent blood work did not return anything to be overtly concerned about, and he’s still drinking water.

Just wondering if anyone has noticed these changes in their dog as I think about his quality of life and end of life planning eventually.