What does "developed on a 5x5" mean? Do you mean that they were printed that size? If so, who did it? It might just be bad printing. In particular, a lot of labs now print B&W by scanning the film and printing on colour paper, which does tend to produce low contrast images. In answer to your other question: you won't see all that much difference between 35mm and Medium format at 5 x 5. By 8 x 10 the difference will be very clear.