Admob filrate went down when enabling mediation

Hi, we recently upgraded our admob sdk and in the same update started to use mediation but we saw our admob fillrate go down by a lot.

We were having close to 99.9% fillrate with admob but immediately after we updated the sdk and enabled mediation our filrate went down to around 30%

at first we used admob as the lowest priority showing first inmobi or mobfox ads but the fillrate in all of them was pretty awful (we expected the inmobi and mobfox to be bad at the start but improve over time, but didn’t expect admob to go down) so we disabled mobfox and inmobi and left admob as the only ad network configured for mediation to see if it would improve admob fillrate, but it didn’t improve at all.

This is our screenshot of our report (the real admob one, not the mediation one)

Just for reference or if you are curious, the app we are talking about is:

Thanks for any information you can give us.

Gemserk Studios