I have several winter squash varieties growing here, and it seems they have all gotten infected with some disease.. can you help me recognize the disease please?
the leafs get white lines then begin to dry out..

the plants currently have powdery mildew but I have already pulled out the infected leafs and used the remedy of 1 table spoon of baking soda for 1 gallon of water and sprayed it on the leafs, if anyone knows of this treatment; how often do i do this until the mildew is all gone??

The soil I'm using is sta-green, which is flower and vegetable garden soil and it comes with fertilizer, about 70% of that soil and the rest is regular dirt from my backyard. I live in California and the heat right now is INTENSE, I water every other day and sometimes when it is hot I water every day, i just don't use as much water.