With kallitype I use two separate baths of three minutes each of 3% citric acid. For a 7X17 print I would probably use each bath no more than three times before discarding. Always wash well after development because if you do not the life of the baths will be shortened.
f there is any stain left in the paper after six minutes of clearing in 3% citric acid the reason is most likely that the sodium citrate developer is properly replenished. There is really nothing you can do to remove the stain if that is the case.
Pt./Pd. prints require more aggressive cleaning procedures. I generally use three or even four separate baths of five minutes each of 5% citric acid.