As the MFC performance became further degraded (after t=45 days), two different anomalies were observed in the power density curves. The first was a precipitous reduction in P near the former apex of the power density curve (similar to type M overshoot), and the second was a classic current overshoot at low external loads, Rext < 10 kΩ (similar to type D overshoot). We consider these two phenomena separately and go beyond the usual definition of overshoot (ΔĪ < 0, ΔP < 0 in a power density curve) by quantifying its strength. At t=45 days, the measured absolute overshoot was ΔĪOS=54 mA m -2 , which is equivalent to an overshoot factor ΘOS=6%. At t=48 days, the absolute overshoot more than tripled to ΔĪOS=173 mA m -2 , with a corresponding increase in the overshoot factor to ΘOS=19%. This change corresponds to a more than tripled ΔĪOS and ΘOS in three days, signaling a rapid decline in the health state of the MFC.