I recently almost ruined a DWC crop when my AC died on me, and the hydrogen peroxide wasn't enough to fend off the root rot. I have to say that the combination of sensizym, piranha and voodoo juice saved my crop. It would have been a total wash without them, and the roots have never looked so thick and strong.
Now, i'm sure AN would have you use sensizym and piranha as a week to week product, but to be quite honest, do your pocket book a favor and just use them to treat potential problems... and possibly once every 3-4 weeks for a maintenance dose. Keep your temperatures dialed in, and follow basic steps to keep your grow area clean (disinfect tools, wear gloves, no shoes in the grow room) and you'll often find these products won't be needed. I wouldn't recommend useing voodoo juice more than 2-3 times per crop (once every 3 res changes or so). It's just kind of a waste of money in my experience to be pumping that in every single res change. It helps develop wonderful roots, but you don't need much at all, and very often to get results.