Sandy, you are absolutely right. There is a noticeable (more) brown colour on the negative with the 2:2:100 dilution. As a test once more, I just finished developing in the 1:1:100 dilution two negatives. I made a visual on all that I have done so far and it is clear that the 2:2:100 dilution results in a more brown stain.

I would like to stress how nice PYROCAT HD and Efke PL100 work together. It seem like cheating when negatives like this come too easy.