<span class="link_user">@The_Bearded_Grower</span>, I guess. I have a lot of air flow with 3 fans on high. The humidity was only about 55% usually, except it would go up after watering. I have a little dehu in the tent but I guess it sucks. I only empty it like once a week.
<span class="link_user">@Ezzjaybruh</span>, thanks for your comment! I'm using organic Grower's Ally Fungicide Concentrated. Used 3 tablespoons with a gallon of water in a Vivosun Sprayer, and it was enough to cover all 4 plants making them dripping wet. Next day no mildew on leaves and did not come back. Some of the deep lower foliage sugar leaves mildew still stayed, but I tried not to oversoak the buds so that's my fault for not hitting those areas enough. I'm very surprised how well it worked with only 1 application. It did turn all white hairs brown though, but buds are still growing and producing new white hairs the next day.