Yank out the fan relays and look on the bottom (terminal side) of the relays. Dollars to doughnuts they will have a melted appearance around the base of the terminals. New fan motors and heavy duty relay kit is in your future.
I had several nightmare overheating rides because the fans had overheated the relay sockets resulting in poor fan function. Even after replacing the fan motors, the fan speed was low due to the relay sockets being cooked and 'yawned' out.
Fan motors at Autozone seemed to work fine. They're like $40.
The relay harness upgrade kit from Innovative Wiring was ~$120...