Leaf edges turning brown and curling on my beans with no insects visible

Browning and curling at the leaf margins with dead patches and poor pod filling, appearing after a hot dry spell and with no insects seen, often points to a physiological problem rather than a pest, commonly potassium deficiency or water stress causing marginal leaf scorch. Beans are sensitive to swings between dry and flooded soil. Check the irrigation pattern first, keep soil moisture even with mulching and frequent lighter irrigation in hot weather rather than long dry gaps. A soil test will show if potassium is low, and if so apply a balanced potassium fertiliser, since potassium also helps pod filling. Rule out a leaf disease by checking for spots or fungal growth, and rule out salt buildup if you use saline water. Get a soil test and a leaf checked at your KVK before adding fertiliser, so you correct the real cause and do not waste inputs.