Disclosed are fuel cell architectures, fuel cell stack monitoring systems, and control logic for detecting fluid property changes in a fuel cell stack. A method is disclosed for detecting a flow property change of a fluid in a fuel cell system. This method includes determining, e.g., through system analysis or accessing a look-up table, a correlation between voltage change of the fuel cell system and flow property of the fluid, and determining, from the voltage-property correlation, a calibrated voltage drop corresponding to the property change of the fluid. The method monitors system voltage (e.g., moving average voltage of the fuel cell stack operating at steady state), and detecting a voltage magnitude change in the system voltage, e.g., when an anode exhaust valve is opened. Responsive to the voltage magnitude change being greater than the calibrated voltage drop, a signal is generated indicating detection of the flow property change.