HELP! Yellow Mottling on Leaves

[Tone22]

Hi All, one of my plants (Red Diesel) is getting yellow mottling on some of its leaves. On the leaves affected there are grey spots on the underside. Initially thought it was nute burn but flushed 5 days ago and its getting steadily worse. Just entering 6th week of flowering, buds look fine. Any thoughts please let me know. The other plant (Tangerine Dream is doing great). Thanks everbody

 

[Lashdog]

I think that's normal, plant is moving nutes from leaves to buds.

 

[Canuck147]

Not sure if it is your lighting but your first pic looks like white powdery mold to me.

 

[Bengfan]

Being that you are 6 weeks into flower it is most likely normal but I would put a scope on the underside of those leaves and look around for insects for my own peace of mind. Good luck!

 

[Tone22]

Thanks everyone. Still a mystery this one. Temps are 70 night, 78-80 day, feeding it canna terra flores and gave it some cal mag today, just in case. I can't see any bugs on the plant or in the soil, plus the other plant is completely unaffected. There are spots on the underside of the leaves, which will not wipe away so think not mold or eggs. Pic below of underside of one of the worst leaves. Development of buds has slowed. Thanks again!!

 

[duckman]

hard to tell from the pics but maybe https://www.growweedeasy.com/cannabis-plant-problems/yellow-leaf-spot-leaf-septoria is worth a look...

 

[Bengfan]

It does resemble thrip damage. Do you have a scope, loupe, magnifying glass or something similar to use to inspect leaves(especially underside) for insects? They are very small and almost impossible to see with the naked eye.

 

[az2000]

I agree. But, it seems odd his other plant doesn't have it.

To me, the first photos look like salt buildup in the soil, overfeeding, lockout. It's possible for one plant to eat less than another. If the OP didn't water/feed with enough volume to get much runoff, then that plant could have a problem while the other doesn't.

But the later photo of the underside of the leave doesn't look like salt buildup/lockout. I've never looked at the underside of my leaves when I had salt buildup/lockout. But, I don't think they looked like that. Maybe they did. The backside looks like a pest. But, that takes us back to why one plant is immune.