if ur in flower already then u are too late to avert a mildew infection... the plant is infected for 1-2 weeks before u ever see the spots form on the leaves, which is why it seems to pop up everywhere all at once and that removing leaves does little do slow it down.
Serenade is OMRI listed and works extremely well to kill the infection from the inside, never use anything during flower, only veg and never flip the switch till they are healthy and recovered
most importantly tho is to make ur room uninhabitable to mildew.. which means keeping humidity low, ventilation high (4:1 exhaust to intake for negative pressure) keep ur room above 76*F, 78 is ideal. also make sure ur roots are not dry while leaves are moist aka humidity is too high also clean clean clean clean clean ur space! always wash hands and wear clean clothes! and ALWAYS take ur shoes off before going near the babies