I assume you've used this particular chemistry before without problems? Were there any undissolved bit in the chemistry? Otherwise, there doesn't seem to be anything unusual with your chemistry, so I doubt that's the problem. I'm guessing, of course, but I think that the hot water rinse is the likely culprit here. If the water were hot enough (70 to 90C is plenty warm), the rapid cooling of the emulsion with the stop bath could have induced reticulation. The emulsion literally wrinkles, but I've never heard it described as "needle like crystals."