I have been experiencing some streaking lately (the last two developing sessions) using BTZS tubes, Efke PL100 and Pyrocat HD and would like to hear what people think may be the cause of it. The streaks range from thin lines near the sides and/or a wide stripe around the middle of the film. I have experienced this in two of the last eight sheets I have developed. I certainly keep the tubes rolling in water fairly consistently and I use enough developer (I fill the tube cap to the water line, about 250 ml). In both cases the film was one of two of the same scene from the same holder (the other film being without streaks) so I do not think it is related to my taking procedures. Thanks in advance.