A method and apparatus for detecting oxidation in at least one planar fuel cell stack that includes a multitude of cells is described. The height of the stack is measured to determine if there has been an increase from a previously-measured height. Such an increase correlates with the oxidation of at least some of the planar cells. In some cases, the fuel flow rate or airflow rate to each fuel cell stack can be adjusted, based in part on the oxidation detection technique. A power delivery system with at least two fuel cell stacks is also described, and it includes a stack height-measurement system, a health monitor for the fuel cell stacks, and a load balancer or airflow regulator.