Nige,
I always let my PMK part A cure for a month before I start to use it. I presoak and develop and water stop and fix. Then it is off to the wash for 20 minutes. Now depending on which film you process, the stain is as Don said a yellow green to a coffee brown (Tmax) Fp4 doesn't exhibit as yellow green a stain as doex Tri X and Hp5+ in my opinion. I think you are ok.
lee\c