I use a HP Procurve 1810 switch which is managable, everything is still untagged in the default vlan.
Anyway now it's working. First I checked the physical nics again and found one vmnic (on the already working hosts though) on 100 Mbit but still on auto-negotiation. I set it to 1000 Mbit which could be established and back to auto - still working. I don't think that has anything to do with the prob, but good to see that fixed as well. By the way a few days ago on my vSwitch the adapters were fine, I think the degration happened while the vswitch2vDs migration.
The step that helped was to go to my 2nd vMotion PG and change the dv uplink by another uplink port. After I saw that both vmnics were used I changed it back and it still worked. It seems that the vDs or my host had a hickup as I added the hosts vmnics to the vDs/created the 2nd vMotion PG.
However thanks for your answers!