The "haze" is reiminscent of fungal growth that I've seen on an old Canon FD 50mm, starting at the edges and working its way inward or around the lens. From the image it looks like that. Stopping down the lens about 3 f/ below open will concentrate light through the central axis, thereby "missing" the haze/growth, but a 'fuzzy' corner may still appear. Strip the lens for a "Spring clean".