I don't know what kind of foam (open cell or closed cell) your wings are made of, nor the type of sheeting (balsa or light ply) in the areas that are problems. However, all of these materials shrink and swell depending on temperature and humidity. Most people are aware that wood products swell and shrink but plastics also move. Even with a good finish on the exterior which would prevent moisture penetration, the exposed cavities like wheelwells or even wingtubes can allow moisture in. Even in a completely sealed watertight vessel, changes of temperature can generate condensate. Wood products shrink and swell at different rates depending on the direction of the grain. Plastics change in a uniform rate in all directions...yet if a plastic component is 3 times longer than it's width, it will apear to grow proportionally more in the direction of it's length. Your pictures seem to show areas where different materials, different grain direction, or different thickness components are mating and in some pictures it looks like the butt splice of different sheets.

Like the above suggestions, thicker glass cloth and resin coat would create a firm shell that would not be as affected by the substructure changes...you built light, which has it's advantages but you have discovered the down side.