It looks like you might have pests. Look closely at the bottom of the leaves. Hopefully nothing's crawling about. Do you have a way to magnify? Let's hear some more info: soil, nutes, ph, RH, temps etc
Its in a closet with main fan inserting air and one more fan pulling out air.
So more info: the soil is mixture intended for growing, temps are pretty good its not so hot inside and there is air movement I think around 30-25 C temp.
the ph is around 6-6.5 mix with nutes.
I think last week I put one more spoon of nutes inside the water, normally I put 1 little spoon for one litter. [according the guidelines on nutes]
Today I changed the water and put it normally.[with the recommended values]
It may be the reason for this?
Also, How I check for pests? I didnt see any.
You said there is air movement "I think" which says to me that you don't have an exhaust fan, which says probably powdery milldew. Insecticidal soap spray or whole milk spray will control it but once it's in the plant it's always there, unless you can clone dip in out.