Higher dose of gonal but slower response ?

I am on my third round of ivf no transfer as yet... due to genetics... First round was 200 gonal and I ended up with 8 eggs collecting on day 13.

Second round upped meds to 250 gonal and retrieved 15 eggs, collected on day 14.

This round we have upped gonal to 300 and added Luveris for egg quality... BUT the response is slow... on the day 11 scan, of the 16 follicles growing, only 4 are size 16 and 2 are size 18... I expected to collect on fri (day 13) but now going for a third scan and bloods on day 13 with a view to collect on day 16 which is later than normal....

I’m confused that whilst there is “more” they are so slow to grow in comparison to day 11 scan last time on both rounds ... particularly when the gonal amount has increased. Has anyone experienced this ??? Can they catch up ??? Or is it just a poor response this time ?