I would make-up a disinfectant solution in a pot.
Chop the worst affected leaves off and remove to airtight bag, dipping snips in your disinfectant between each cut.
Take out as much infected leaf (more than 25% 'powdered') as possible to increase the airflow. Add another circulating fan.
Run a dehumidifier to get humidity below 40%. Beware high temps at low humidity.
Make up a solution of essential oil fungicide using 3 of these: ginger, cinnamon, peppermint, pine, turmeric - 20 drops/litre total + neem oil + natural soap. Paint the solution onto remaining leaves after 'dusk' once per week til harvest. You could incorporate a silica product too but havn't tried that myself.
I would'nt be using any chems on them this late into harvest.
After harvest comes the clean-down. You have to be real thorough on every surface, all ducts, pots, reflector - every piece of equipment in there gets a thorough clean with bleach solution - just imagine millions of microscopic mildew spores and take them down.
Fumigating with sulfur dioxide will also do a thorough job but is most effective at concentrations plants cant handle so best used after harvest. It can tarnish reflective surfaces so not so good for tents and mylar rooms.
Then when you restart (preferably after a short fallow period) keep up a weekly preventative spraying regime with silica, neem and essential oils.
I just came across a biofungicide called AQ10 which is supposed to be an effective preventative you could try next round.