Last night I developed a 35mm film in my usual way - Neopan 400 in Rodinal 1+25 for 4.5 mins, Ilfostop, Hypam fix, wash and air dried. Nothing different from what I normally do. When I looked at the dried negative through the focus finder the whole film was covered in a maze of tiny cracks like crazy paving, which made the final print look really grainy. What happened - what did I do wrong?