Nylon is one of the easier carpet fibres to clean, (stains can be a different matter). There's more to cleaning solutions than "strength" and pH, but i'd expect good results on nylon with even a poorish pre-spray.
Your choice of regular pre-spray is excellent as it is Woolsafe Approved but is able to deal with most soils on most carpets and fibre types. Saves on a lot of changing of solution for different needs. I find that a freshwater rinse, as recommended with Spitfire Advanced, is a great selling point. And at 1:30 it's economical too.
I have found the Prochem products to be excellent and will still use them as the need demands. But as you have found from this experience Rich, you were using a sledgehammer to crack a nut, and the results were good, but not better than your usual, more gentle approach
Safe and happy cleaning

Ken