If the port wheels are down, the only thing that can allow that is a loss of hydraulic pressure on that port landing gear. Hard to tell from the picture, but weight alone (fuel in the port wing and none in the starboard tanks) won't sag the wings that much on a Herc. If I remember right, the ones I have worked on held around 67K pounds of fuel (full tanks) but most of that is in the center tank, not the wings, similar to most every other aircraft. And the furthest outboard wing tanks hold the least amount of fuel compared to inboard and center tanks.