withering leaves on climbing french beans

Hello,
Climbing French beans sown in pots early june and into position ten days later.
Beans are now top of their frame 7ft and developing flowers etc etc  all looking quite good EXCEPT >>>
Some ( not many)  of the leaves have withered ,colour yellow and brown ) Is damage caused by a bug ? or maybe too much watering during the hot spell...... should i remove the infected leaves ?  Your advice welcomed
Thanks
KP