Brown rust spots on leafs

[Newgrower256]

Hi,
My autos are 7 weeks lots of brown coloured rust spots appeared overnight. Mainly on the top leaves, also got red stems but been like this for weeks the spots only just appeared. Been looking and maybe a calmag deficiency so added some today.

Any ideas?

 

[Sativa1970]

Couple things can cause brown spots. Key is where they are on the plant, where they are on the leaf, and the color fade and shape of the spot. Yours is not just top or bottom so not nutrient. All are a single color tone so not fungus. Perfect round spots so not chlorosis. All on one side of the plant,,, spillage. Were you foliar spraying or splash water on the leaves maybe? Water droplets will act as a magnifier on leaving round burn spots. Foliar spray can puddle into a drop on the leaf and leave a round salt deposit as it evaporates causing spot nute burn. This all happens more often on the back side where there is less ventilation and hard to see until it discolors the plant.

Be aware of water drops on it to see if it gets worse. The leaves will not go back to green.

 

[Sativa1970]

Just looked at the pictures again. Check the under side of those leaves for vary small specks that move. Ideally look with a magnifier.

 

[Phytoplankton]

Normally, a cal-mag or similar deficiency doesn't have the "round spot" look and the leaves overall don't look healthy. These leaves look very good other than the spots. The cal-mag won't hurt anything, and could help. The spots appear to be very uniform in shape, which leads me away from a deficiency, and more towards a water droplet issue. Even bug damage is usually are not that uniform, but I'd do as @Sativa1970 says and check for critters under the leaf. Do you mist, foliar feed, or have you sprayed anything on the plants recently? I've had black spots on outdoor grows that later turned brown from bug poop, but this doesn't have the same look.

 

[Newgrower256]

Checked underneath the leafs and nothing, now you've both mentioned it I feed them just with watering can but spilt some on this plant last time didn't cross my mind but think it probably is burned from water droplets.
Thanks

 

[Phytoplankton]

I think you're correct, it is a very nice looking plant! Keep an eye on it, try to minimize water drips on the leaves and see if the problem doesn't go away.