I do not think that you have much to worry about, lightly used brushes shed a bit. To give you an idea, I recently bought a new brush but not a Rooney. It did not shed a hair in the first 2 or 3 weeks but then it started shedding. Since I started counting, it has lost 29 hairs in 14 non consecutive days, this is an average of 2.09 hairs per/day but the brush did not shed 4 of those days, which brings the average to 2.9 hairs per day when it shed ;-). I am evaluating the process. The funny thing is that when I think it is done losing hair, it starts again ;-).
Al raz.