You may get better results by changing the acid in the pre-treatment step. More on this later, stay tuned - I have a friend with good news for all of us...

BTW, is it develop-out pd or print-out pd? If it's develop-out pd you may have problems with the ferric oxalate (FeOx) solution; to my knowing, aged FeOx solutions are prone to staining...

Regards,
Loris.