Yes it is normal. Every time u get promoted to a higher level, ur players lose a star. Their Q remains the same but one star is reduced. The reason is that the star is an indication of the players relative quality to other players on that level. Like for me at level 8, a 5* player is b/w 55 to 59Q while for a level 9 player, a 5* is b/w 60 to 64 and my 5* appears to him as a 4*. It takes time to understand but if u get it, u will know it is totally correct method.