I am well accustomed to data tribal customs so believe me when I say this is very very normal. In fact it stopped during Taliban control because tribes were busy getting killed by ttp. So this fight is a sign of return to normalcy.
That said, usually when such fights happened in past, FC would jump in within 12 hours as a neutral force and fighting would stop. It gave a face saving excuse to both sides to stop fighting, but with army and fc busy fighting, this clash will go on longer with more casualties.