I've had trouble with BLIX and pink stain (especially the pink staining of STAB) for many years and came to the following conclusions:
- Pink stain is not the end of the world, five year old slides that turned STAB pink still look fine today.
- Pink stain becomes worse if BLIX is not freshly mixed and/or has been used a couple of times. PE recommends extending BLIX times by 50% over the BLIX times given by Tetenal's instructions.
- Warm wash water removes pink stain much more effectively than cold wash water.
- An effective method to get rid of pink stain is filling the film tank with warm water and letting it stand for 20+ minutes. No agitation is required, so you can develop the next roll or do something else in the mean time. The wash water will have a strong pink cast when you pour it out. Do this a few times and the pink cast will become weaker and weaker, until you pour out mostly clear water. Once that is the case, proceed with STAB and drying.