Karen, I would use at least 3. The Color Catchers do work, but my DH had an entire load of pink underwear to attest to the fact that they are NOT perfect. In fact...if it was my quilt...I might even wad up some of the colors that I think might be offenders and wet them in a bowl with a color catcher in it just to see what happens.
Candace...great to see you back!
Kathy, another gorgeous block as usual from you!!!