I also use a Nova 16x12" unit and have just cleaned it out after several months; the developer was quite brown and bleach-fix had some sulphur floating on the surface. I make up the stop-bath from a formula supplied by Champion Photochemistry with 80% Acetic Acid and Sodium Suphite anhydrous to make 5 litres.The developer is Champion and the bleach-fix is from Photomart.