What Causes Metallic Taste After Coughing With History Of Pneumonia?

woke up with a cough that tasted metallic... have been pushing fluids... sputum is clear to maybe just a bit yellow. no other symptoms.. several years ago i had pneumonia; am i prone to get it once i have had it? I have been dieting and taking lemon water every morning, so i have a lot of vitamin C in my system... could this be part of the respiratory flu that is going around. I have very little exposure to people since i work at home and go out for church/groceries etc. Thank you...