I've just souped up three rolls of Tri-x in 35mm and 95% of the frames are extremely flat and around a stop under-exposed. I used my standard times with XTOL 1:1 @ 9 min. Everything as per normal... camera is fine, metered with a handheld which is accurate. I also shot many rolls of Portra using the same camera which came out fine. Only 'new' thing was a light yellow B+W filter so I exposed everything @200. My only conclusion is that my XTOL has expired.. it was just a little flakey so that should have warned me I guess. Its been stored properly at full strength for about 6 months. Could expired developer explain very flat negs? I don;t think I'll even try and print these... lessons learned! ;-) Any advice appreciated. Thank you.