I tried to donate blood today, but the person with the ARC said that my blood was just trickling out. Someone came to assist, but it didn't help. Consequently, air got in the line and they stopped the donation saying that it was now contaminated. I noticed the last time I gave blood that it seemed to take longer for me than for others. (Several people who started their donation after me left before me.) What may cause this? Should I be concerned? Thanks for any insight you can provide!