Brow shock loss
Hang in there...this sounds to be normal recovery as native hairs in brows will undergo a degree of shedding post procedure. If your brow hairs shed within a month or 2 of your procedure, this would be more trauma caused by the procedure. If they are shedding now, most likely this is due to normal growth and recovery post procedure. By month 8-9, you should have regrowth of the lost brow hairs if they were not traumatized intraoperatively.
Native hair shedding after transplant
This can happen in some cases which is known as shock loss. It can also happen if your doctor was not careful and damaged the native hair follicles during the creating of recipient sites. I would recommend following up with your doctor however in the meantime you can try using some latisse or rogaine on the brows.