FWIW, I was mixing Pyrocat MC A5 +B5 +100 and it wasn't doing its job. I was actually mixing in that order and the developer went off. I reversed the sequence, e.g., 100 H2O + A5 +B5 and all was well. Mixing the concentrates first did some weird things. Don't know your mixing sequence but if you are doing it in the order you described, you might want to add the concentrates to the water.

YMMV,