I've actually super setted dead lifts with Incline barbell press for a few weeks when I was super setting back and chest together and it had no effect on my strength. Actually I was getting stronger on both exercises week by week. It could be your CNS or conditioning. I would also focus on proper nutrition and rest because dead lifts are very taxing on your body. Also I've found that stretching and light cardio tremendously speeds my recovery time. If it's seriously that taxing on your body I would consider using a little less weight or doing less overall sets.
Anything worth having is never easy to achieve.