New Grower Here Looking For Some Help Please. LEAF DISCOLORATION

Hey all,
Recently my buddy started noticing some of his leaves getting these light green patches on them, he doesn't know what it is, and neither do I. Over all the Plants look super healthy, nice dark green leaves, and thick stems, the only thing that appears to be wrong is the weird discoloration. I looked on the internet to see what I could find but had little to no luck, I am thinking it may have something to do with the nutrients? could anyone on here tell me what it is? I have included a picture above, I apologize about the poor quality, it was taken with a cell phone. Any input would be appreciated, Thanks.

Check your pH... make sure its not the beginning of lock-out

looks like the tobacco mosiac virus. i wouldn't sweat it, i had a few leaves look like that and nothing ever happened.

Thanks Guys, Unfortunately my buddy does not have a PH tester due to the fact its a budget grow. I did look up both suggestions and I'd have to say it looks like and has the symptoms of the Tobacco Mosaic Virus and I'm thinking that's exactly what it is, that's too bad because these plants were seeming very promising, I guess ill tell him not to clone these plants for the next grow, he's going to have to hunt down more clones or start from seed (which is a pain in the ass) thanks for all the help guys very much appreciated!

like i said, i have had a couple plants that has had them type of leaves and i have yet to have or see any big issue in growth or yield when it was all said and done.

From what I read online it says its not the best idea to keep it going because all you're doing is spreading the virus, as a last resort if they finish well they will be kept going, but he'd much prefer having 100% healthy plants. Once again thanks for the help guys.

I'd say its either to cold in your environment or tthere's not enough air circulation or both