Bob, Jim, thanks for your answers. I have also considered that
possibility. In fact, washing water was particularly cold that day, 11C
(around 52F), and then washing after KRST may have not been
enough.

However, if there had been fixer left in the print, wouldn't the stains appear
in the ferri bleach, regardless of the gold? But the stains only appear
with the gold toner - and before the last fixing bath -, and only after thiourea.
Besides the pictures in my post, I have a few other examples (processed in different days),
with the same pink spots, again, only if gold after thiourea was used.

Anyway, I will be more conservative with the washing step.

Thanks!

Pau