There’s spots on my leaves , I have no idea what it is , has any one seen this before. It’s spreading , it starts as a light spot than browns and mostly stays on the veins of the leaves , is it to much of somthing ?? Not enough?? , I give cal/mag and flower fule, the ph is good and my two other plants get the same regimen and are growing fantastic . I increased air flow and cut out all affected leaves which helped air flow , could this be fungus gKant bites??
The larvae of Fungus Gnats attack and eat your plants roots, have you got a photo in natural light of the whole plant, and any other info, grow medium, nutes, are you using a PH and PPM pen?
More info you give us the easier it is to help you 
@blackthumbbetty and @latewood may have a better view on your problem.
Looks closely on the bottom of the leaves for bug/mites.
I had mute lockout , it was showing calcium def there and nitrogen shortly after so I flushed out my pots waited an hour than I gave a dose of my new fertilizer mega crop and megazyme I have the whole nutrient line now I’m trying and they are completely recouped . It was from using low quality ferts when I ran out of good stuff