Can anybody tell me what these spots may be?

[Mmdoug]

Hi, doing DWC plants are a few weeks away from flowering stage. Some of the leaves are getting light brown and yellow spots on them, they’ve just started in the last 36 hours. I have them under 24/7 light, I keep the temp at 21c. Any input or suggestions are much appreciated!

 

[Buds Buddy]

Are you using Cal Mag ? Looks like the start of a Cal Def.

 

[013]

What are you feeding them? What do the roots look like? White, stained, slimey…. Got pics?
Are you using an enzyme like hydroguard or Z9?

looks like you are getting a lot of light into reservoir thru perforations in the netpots, weed roots love air but not exposure to light……

welcome aboard Mmdoug

 

[CharlieWaffles]

Looks to me like she needs cal-mag.