Problem: In theory, when you drive forward, the mass of those blades will want to move back, therefore lifting your wedges off the ground ever so slightly (but ever so slightly can make a big difference, as I've seen on several bots before.) I've noticed that it's generally not a good idea to put a lot of extra stuff on the same burst motors as your wedges, unless you can stabilize them in the back so they don't lift off the ground. Perhaps try putting some short extenders touching the ground underneath those blades.
However I'm making a big deal out of a relatively minor problem. That's a great bot. So is Serious Cat; you're a very fast learner.