https://bitcointalk.org/index.php?topic=5289066.0Low 40's is normal for the 1080ti and it will only get lower due to a known bug suffered by the 10x0 series excluding the 1070ti where it was fixed.
1080Ti has gone from 55 to 43mh in 5 years and 1070 has gone from about 33mh to 25mh.
It was not fixed with the 1070ti either. Used to get 34 mh/s easily with 1070ti cards. Now they are getting 29-30 mh/s. Meanwhile my RX580 cards happily mine at a little over 32 mh/s. They actually improved over the years. The 1070 cards also lost hashrate.
The 1070ti lose hashrate with DAG´s above 4GB, it was lightly better than all other Pascal GPUs. All other lose hashrate above 3GB DAG size.