I'm experiencing an unpleasant problem with some of my prints. Some areas of the photo come out lighter than the rest of the print, leaving an ugly stain effect. These stains are very random: they vary in size and shape; there does not seem to be any correlation with specific paper (I'm using RC papers) or developer brands; they appear on one print of the same photo but not on the second print (if I'm lucky). I thought it could be uneven development due to uneven immersion or something like that, but neither placing the paper face down in the developing tray nor increased agitation have helped. Does anyone know what causes this problem, and how to remedy it? Thanks.