Hey, go to your local garden or hardware store and buy some sulfur powder. It's usually marketed as a fungicide for grape vines or rosebushes. Mix a scoop of it with water in a spray bottle and give your plants a good spraying (after the sun goes down). You need to take care of that powdery mildew on there. Or if you happen to have copper sulfate lying around somewhere, you can use that.
As for your watering question, it's not about watering every X number of days. If the soil is still moist, you don't need to water. If the soil is all dried out, then water em.
My roommate in college used to go into the grow room and water the plants, even if the soil was soaking wet. Drove me fucking nuts
