Weird Spots On The Leaves - Please Help

I first noticed the spots on only 1 leaf about a week ago and it has since spread to a good percentage of the leaves now. I wasn't worried at first, thought it might just be dusty or something but now I am very concerned.

It is raining so as soon as it stops I'll snap and post some pics.

Does anyone know what it could be and how I can reverse or fix what is happening?

I would really appreciate some advice and help with this. I have been babying my plant and really putting in the time to research and gain knowledge on producing the best plant possible. I would be so sad if something happened now this far into the plant's life.

Thanks in advance!

Delta 9