The usual answer is to simply develop longer. Your negative will be a bit more dense and also more contrasty. I don't have enough experience with Pyrocat-HD to tell how well it responds to changes in development time, but all film-developer combinations do respond. Some, however, respond a bit differently than others. Your technique also strongly influences the results. Many people consciously develop for low contrast these days, and the traditional zone techniques often do not work as well with those techniques. Start with dilutions and agitation regimens that are designed for normal processing, and then develop longer. For your problem, I would look at some zone development recommendations for your film and apply a N+1 or N+2 correction as you see fit. This may mean trying a more conventional developer like D-76 or HC-110 for these particular shots.