Pedant's corner: Jane BOWN FLUORESCENT
More to the point: Are you using HP5+? You don't say. For this film, I agree totally with Mick about the meter setting (I actually use 250) and dev time (10.75 minutes in D76 1+1 for average contrast subjects). Unless you have extensive experience of Pyrocat and its keeping properties, you are adding to the problem by using this dev, although apparently it was still alive and kicking last week when you did some sheet film.
As regards exposure under average room lighting, again agree with Mick - 1/60 at f2.5 to 2.8 should be close. Since fluorescent lighting is usually even, a reflected (center-weighted or averaging) meter reading will be accurate, also an incident reading of course, the lighting as you say is very flat so additional development time will not hurt. If you attempt to meter for shadow and place this on zone III (i.e. close down 2 stops from the indicated exposure) don't meter a shadow on the floor, this will mislead you into overexposing 2 stops or more. Since you are presumably interested in faces. meter these, as other have said, and open up 2 stops from the indicated exposure for Caucasian skin to place the skin tone on zone VII. Agree that it sonds like an underexposure problem.
Regards,
David