Pictures would be helpful. Curcurbits are prone to mildew and disease. But aquaponics can be difficult to get the nutrient levels correct as well, so either could be your problem.

Yes âÂÂCole_RobbieâÂÂ, you're right. I totally agree with you. But really image will be helpful for us to give you a suggestion.

The problem of leaves getting âÂÂcrispyâ feeling and with white or molted yellow tips; is because of the spider mites. Have you used the nutrients with proper measurement? If yes, then they are not proving to be beneficial. So, use some other product best suited for you.