Powdery mildew

Even with crazy amounts of watering (5 10L cans on my garden cart, between 10 and 15 trips back and forth every other day), plants are now really suffering from the sustained dry spell.

My courgette plants have powdery mildew. I generally cut the affected leaves but I decided to pull out the worst looking plant ('Bianca di Trieste, the 1st one to produce a prolific harvest) and sow a new courgette seed in situ. I've had successful results in the past and, when plants start to struggle, it's generally best to start again.