I started reading yesterday and read that 'burn marks' on leaves get there when osmosis goes the wrong way: out in stead of in. In the book it says it can happen when too much nutrients are dropped on the leaf...
Maybe it is because of the fan, if you move a houseplant to a new spot they will get a shock as well. Maybe we should just wait and the plants will come around sooner or later. Because the fan apparently ís important.
I got this book of 780 pages
Handboek ecologisch tuinieren - The belgian bible of organic farming, 780 pages.