I just bought 3 new brushes from the tack shop. I got a stiffer natural hair brush, a really soft natural hair brush, and an Oster soft brush. I was brushing my horse with them and they worked really well but they left some bristles on him. Not clumps, just one or two here and there. I tried pulling some out but I got a few but not a whole clump. Is this normal for this to happen?