Gday about depth of field.
It's proportional to aperture, distance, and focal length.
At your distance I'm pretty sure it would have been in focus at wide open.
Check dof master website, google it, and learn some sample values.
Also, just like one doesn't run a marathon with brand new shoes, one should never go on cold turkey and move to a new camera just before a holiday without learning it's strengths and weaknesses.
I had my 6d 3 months before going to Egypt. And I when I buy a new lens I learn all I can about it. Resolution chart, vignette, dof., flare, color. Etc.
This way I will never find myself at a critical situation wondering what just happened.