The dark specks are BENDABLE? WOW. I was going to suggest the dark specks could be blood because that is the way that blood shows up on a urine test strip. I cannot imagine they would be that "tough" though.
All I really came to say was that the B vitamins tend to color the urine that "neon yellow", at least for me. I wondered if that means I am peeing most of it out, and not absorbing any [because I didn't need it, it was extra? - just a guess]?