best ways to get rid of white powdery mildew?

[Cottonballs]

So we have been dealing with mildew since the end of summer and we have tried a ton of remedies from adding fans, better circulation, and a foliage spray of baking soda with olive oil to name a few.
Now in our tent a few plants are getting mildew with the rh sitting at 40-50 roughly. We have a few fans in the tent to circulate air but they are not intake/exhaust fans yet. I know this is not the best way with a tent, but spending that kind of money for a fan is out of the question with my wedding coming up.

My question is, we have a second 600hps set up ready to use and are only using one for the flowering tent. Would adding the second light be the best way to make the mildew go away since it would add more heat? We are sitting around 75-80 so there is room to go higher but I don't know how else to get rid of this mildew. I am going to get neem oil next but any info helps, thanks.

 

[cannilingus]

check out one of the sulphur burners. i have one. along my house, is bamboo, and honeysuckle. they and pm are best buddies. anyway, i used the sulpher burner. fans off lights off. do when lights are out. for 3-5 hours. it will smell like a million matches were lit. and, if your plants are near harvest, i would not do it! could end up making them smell funny. anyway, back to the sulpher. repeat this for three days. mine went away, and has not returned. i paid like near 80. for the burner, and bag of elemental sulpher. if you get the digital one, its a sloww release, and uses these yellow kernals, that form a flat, after heated. the other kind, seems to burn the sulphur all at ounce. wow. the stench. lol. but, it worked for me. maybe you can borrow one. offer to buy him some sulfur.

 

[Cottonballs]

That is a whole new level of extreme there. Sulphur can be toxic to humans if it's enough, that would be the last thing I would try.

Does anyone have any other input, like adding an additional light?