Light Burn or Deficency

High my friends,
Just ja quick question.
Can you identify what lead to the yellow brown spots on my leads.
These girls are different strains 4 weeks into flower und around 400w 3500k led/1,44m2
They are all bio and only get ph corrected almost RO water.
The soil ist conditioned with some bio adds
The temp is around 24c and RH 65%

I had the lights powered up to 500w because of my ne ppfd meter which showed 700umol then but turned it down again.

Any ideas
I guess it was the to strong light but I'm not sure

Would love some ideas

Thank you!

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Could be just a natural aging process - the fan leaves start giving up their stored nutrients to help flowering buds.

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Interesting, what did you spray 'em with?

Yes ok that would make sense
I used some spray against spidermites but just for prevention. Didn't really saw any. But I used it 3 weeks before I took the picture.

I turned the light down now for severely days and the problems did not get worst .
I think it was the light

I guess the recommended maximum around 700umol is only possible at a perfect vapor pressure deficit at around 26°C.
550 should be enough in my case I guess because 23.5 is the max temp I can reach.

I think 65% RH is a bit mucho to be honest is that next to your pots or above your plants?
Also 550 umol/s for flower seems a bit low.
The plants should be able to handle 600-800ish umol/s.

Can you see the white thin the air on the second picture
That's the sensor which says 65%.
In the attachment you can see the VPD chart which says 65% is cool at 23-24°C

65% RH = playing with fire, brother.

I know but I can't get any lower

Light burn would affect the parts of your plant closest to the light.

But what is it then?
Yesterday the yellow spots got a bit more intense again :s
Do you think it could be Potassium Deficency?
The plants are quiet big for there pots

Maybe you have a big humidity change in day and night cycles.it causes weed to " cry" on the edges of the leafs making small drops of water.with light too close it becomes a magnifier glass and burns the leaf

Also what are those black spots on the leafs, bugs?

The black spots is just some soil
There is another veggging level above the flowering level and some fell down

I checked the night humidity and it's around 70 which is pretty high to
Guess I have to invest in an dehumidifier :s