I'm leaning towards scrape the top dressing off, giving them a big drink, and possibly using a softer light until they recover.
But this is a tough one OG. Because you don't know for sure what you have.
Sorry I'm a little stumped TBH
First thing I thought was soap burn too.
Then once you updated, it looked like phosphorus to me. So I searched it out.
It could be either, or both.
I really don't think it's lack of nutrition either..........
Something is toxic for your plants.
Best of luck dude.
Keep updating.