That's so great that you were able to dislodge plaque with just lemon water and clean diet! how cool! :)
The P&B drink certainly can't hurt, unless you're allergic to psyllium, which does happen.
I thikn now that you've got most of the plaque out, the shakes will simply help to get the rest of the gunk out all along your digestive system, AND strengthen the colon so this kind of thing doesn't happen again so easily.
Fiber is most always a good thing to have and we rarely eat enough. It forces fats and toxins out thru the colon rather than letting them recirculate. Cleansing is cleansing, it helps without being drastic.