Allotments 4 All

First year growing runner beans so have no idea what is causing this problem, but went down to lottie last night and noticed that the leaves of my runners have started to get tiny holes in them.  The holes appear in the middles of the leaves, not at the edges.  The runners are not very big about 1ft to 2ft high, look healthy, have been growing since I put them in.  I cant see any critters about except for an odd greenfly (now squished) and a few tiny orange spider type things.  Could these be causing a problem?  Not all the plants are affected and not all the leaves - just random really; and the dwarf frenchies which are nearby are fine.  Is this something I need to worry about?  Am I going to get to lottie in the morning and be stripped of beans?  Anyone any advice?   ???

Flea beetles?