lets see,
see if there is anything odd in the gas tank.
that includes, water, bad gas, poor gas mix of ethanol, sand, grit, some other thing that might jam up the pump.

next would check electrical connection, and the line back to the battery to see if there is some sort of frayed, pinched lines that might limit the amps back to the pump.

next the pumps themselves.
are they from the same batch?
do they have something wrong with them that might cause a short inside?


same batch would lead me to believe they might have an issue with that batch, and I would get a replacement from another supplier.