Low resolution with i-tec USB 3.0 + Surface 3 Pro

[KOHLFUERST]

1920x1080 is the maximum resolution I can run on my 2 extendend screens with i-tec USB 3.0 on my Microsoft Surface Pro 3. Funny Detail: this is my second Surface as the first one has been exchanged by Microsoft. With my first Surface I had much higher resolution.

What went wrong? What to do next?

Technical:

i-tec USB 3.0 Dual Display Adapter Advance
Microsoft Surface Pro 3 i7
2x Benq BL 2410
1 DVI-I
1 SUB VGA