Leaf discolouration, is it fungus. Please help.

[Christoff]

Hi there, I found this strange discolouration on a leaf one day, then it spread to another.  At the moment its effecting about ten leaves, old and new doesn't seem to make a difference.  It has also spread to another plant.  What is it?

(top of effected leaf)

(underside of effected leaf, looks normal)

Many Thanks

Chris

Edited February 21, 2021 by Christoff

[itchybromusic]

i can't get the first 2 pics to load 

 

can you take the leaves outdoor to some natural light & take pics without a cam flash   

[Serrated edge]

I can’t load it either but I’m guessing it’s spider mites ,,,

 

Maybe wrong but looks like what could be  a few on the underside of the leaf.