I'm with Gregcoyote on this one...I like to think of starting/running a successful tank like driving a race car: go too fast and you'll crash.
These products add bacteria to the water column, but it takes time for the colonies to establish in the rock and sand. That's why us "old school" folks like to cycle for a few weeks, to give the rock and sand an opportunity to become populated with the BB. If you do your weekly PWC
after you add this stuff, you're removing the BB from the water column, and they may not have had a chance to establish in the rock, causing a mini-cycle to occur.