Start vaping/burning sulfur during the dark period for 6-8 hours in the room with the flowering plants. Just as a pre-emptive cover your ass thing.

Get a cheap light fixture, or a socket that you can mount to a scrap of wood. Put a normal 60-80 watt light bulb in the socket. Take a soda can and cut off the top where you drink froom, and slide the soda can upside down over the light bulb. Seal the bottom with aluminum ducting tape or electrical tape, or even silicone caulking so that the light bulb doesn't shine light outside the can.

You now have a stable base with a light bulb and a lightproof metal sleeve with a shallow dish on top (the concave bottom of the can)

Plug it into a timer, to go on when the lights are off. Make sure it stops 4 hours before the lights come on to give plenty of time for airing out. Even one tenth of a second of HID lights with sulfur vapor on the plants will fry them hardcore.

Put like 1 or 2 tablespoons of sulfur powder in the dish, powdered sulfur is available in any garden center very inexpensively. That should last a day or two. If it is burning more than melting, use a lower wattage bulb.