A dilution of 3:3:600 of Pyrocat-HD is not too weak but you will need very long develoment times. And you must be sure to start with enough developer for the film. I sometimes use stand development for 120 roll films such as FP4+ and TMAX 100 with a 2:2:400 dilution but development times are very long, up to 45-60 minutes. I use a minimum of 16 ounces of developer per roll of 120 film.
Originally Posted by Francesco
You have have also made a mistake in metering the scene but for sure your develoment times are way too short for this dilution.