Lol, always this noob topic at day 1 of the new season.

The quality of your players did not drop, you are promoted and play now at a higher level. The number of stars only indicate the strength of your players relative to level you play. It increased with each level by 5 points, in level 2 it is:
1*: 5-9
2*: 10-14
3*: 15-19
4*: 20-24
5*: 25-29