I think i found out now. Ellie + Drake were played on AT40 2 weeks ago for the first time. Demi got like +5 spins more than Ellie at that time, but on the other hand... last week K'naan and Nelly got a bigger update, but got negative updates in the following days...
So is the update now good or...? i mean of course it's good, but is it good after being played on AT40? I wonder how the update would be if they didn't play her?
anyway LOL first 1m update

Let's see what the next few updates bring!