Whatever is weakening me, here is what a near worst case ride looks like for me; power output about 50 watts low—starts out OK, then steady decline until last 20 minutes just dragging. Heart rate commensurate with effort level; not showing signs of illness. I can have influenza and ride about as strong as this.
After 10 days of Amoxicillin, I am deeply skeptical that sinusitus is the cause, chest xray and CBC are all normal. As I steadily detrain from near all time best levels in March, I am unsure what the 'lemonade' might be. Going on a strict diet now of gluten-free oatmeal, whey protein powder and similar innocuous (had another bloating episode).