Got some white powderlooking stuff on some of my lower fan leafs>

I got some White powder looking stuff on my lower fav leaves, Not sure what the deal is and why this happen..... I orginally thought it was from hard water but my girlz are in flower and I stoped spraying. So next I thought my flow from resevoir to the trays was maybe splashing water on the leaves (i thought this because the area in question is onlower fan leaves). Next I thought maybe Spider mites> still could be maybe at the begining stages, but there is nothing to suggest this on the underside of the leaves, Also I looked at the close ups of pictures I took.

So any Ideas>>>>>>>>

By no means am I an expert but had a similar issue and it was white powdery mold-found helpful info searching in threads for WPM- if it is that fairly easy to fix from what I remember just fix it quickly and the figure out how to prevent more other than that clueless sorry have a good one and gook luck oh wait I think this is the thread hope it helps https://www.rollitup.org/general-marijuana-growing/1469-marijuana-plant-problems-cures.html

It looks like a mold, make sure you have good air circulation around your plants, if the humidity is high stop foliar feeding or spray when the lights first come on to allow them to dry. Wash the leaves with a H2O2/water solution then spray lightly with Ed Rosenthal's "Zero Tolerance". Watch it closely as it can spread quickly. Hope that helps.