Nice, if you can keep that rh in that range it will deff help with slowing any pm growth. On a long flowering strain youd be fine to burn or spray up till about week 5-6. Ideally you dont really want to use sulpher once you have buds but your still in the bud site stage so should be good for a week or 2. Upside to using a burner is it gets everywhere in the room, so it can kill spores that are on the floor, on fans, etc. Whereas spraying your just hitting the leaf surface. If you havent used a burner before do a bit of research so you know what your doing. Make sure All fans and ac, dehums are off, dark cycle obv. I usually wait an hour or 2 after lights off to make sure stomatas are closed. PLug the burner into a timer and set for how long you want on. Usually start with a shorter 2 hour burn, just to make sure the plants dont react weird or get burned pistols, then ventilate with exhaust fan. Want to eventually get to 4-6+ hour burns. I use 2 burners in my room thats 23x24x10 to make sure i get a serious fog in there lol.