Burning leaves

I would say it is the spray. Also why are you spraying them? https://www.biomat-shop.com/en/spruzit-af-schaedlingsfreineudorffflasche-mit-sprueher-500-ml.html This is the product I found online. its a pyrethrin style pesticide. works on a lot of pests from insects to mites to other invertebrates. Depending on what pest you have their might be a safer alternative. Eg. Gnats its best to use BTi or Nematoads, super safer and used for hundreds of years with no ill concern for human health, however the same can not be said for pyrethrin. Also if your spraying when the lights are on that's a no go. Best to spray before lights are on, let it dry and then turn em on, to help offset the RH keep the extractor fan going. Also never spray plants in bloom. If you are going to spray them for foliage feeding, just know its kinda bunk, the best way to feed is via the roots and leaves can only take some stuff in from the underside where the Stomata are.