brown hairs are dead hairs.it could be from pollination or overfertilizing or simply maturity of the buds.It its from pollination its usually a whole sector going brown at once and start curling toward the pod in 2-3 days.If its from overfertilizing it comes after a seriously high EC watering, you would probably know when it was. It usually kill the hairs but don't make the curl backward.If its from maturity the pods will start to swell. It looks like pollination but takes longer and happens at the end of the plants flowering cycle.