This is fairly common to perform under your expectations considering all the new variables you had to deal with. Your trying to feel out the new teammates, approaches, lane surface, oil pattern, oil type, lighting, noise, carpet, etc, etc, etc. Your scores should get better once you put all these distractions past you and concentrate on yourself.
I did the same thing this year. I was better off than you were even in that I had subbed in the league before and bowled some tournaments with my new teammates. But that first night was nerve racking. The good news for me was that I seemed to get more comfortable and had a pretty good 3rd week. Hopefully your results are similar.
Have fun.