Since monday, average dropped to 100GHz most times even lower.
Thanks in advance.

Have you tried resetting the U3's (unplug both power and USB) and then restarting CGMiner?
Yes I have rebooted all hardware.
Removed power and usb cables.
Tried with other cables. All the same.
Plugged USB cables in different USB ports.
No difference.
Most of the time 115/120GHz that is pretty good I believe.
Since monday, average dropped to 100GHz most times even lower.
GHz? Do you mean GH/s? The hash rate, not a measure of frequency.
There is no answer, U3s do what they do, be lucky you have two that work at the same time.
LOL

yes I mean GH/s. Sorry.
I guess I mite be lucky then. It took a lot of trial and error and a decent hardware computer:
https://bitcointalk.org/index.php?topic=827356.msg11803834#msg11803834