Blue blacks can be an indication that some bleach has mixed into your dev. I take it by your post you are not repleneshing your chemestry. I have only used RA4 printers that replenished as they went a long, so I don't know if what you experienced was weak or contaminated dev. You can buy RA4 test strips (small 4"x8" strips) that print out a scae that is easily checked by the naked eye.