Each week, WGT gives you the opportunity to earn up to 170 stars. 140 stars from the daily goals (7 days x 4 goals per day x 5 stars each) and 30 from the weekly goals (2 goals per week x 15 stars each). Be sure to collect any goals you reach immediately. Once a new day starts, any goals you completed but did not collect disappear.
If you only collected 85 stars this week, then you either didn't complete some of the daily goals or you didn't collect them.
You only missed out on 10 credits this week. I wouldn't stress too much about it.