"Damaged" leaves since day 1. Anything I can do??

Specs:

• 3x Auto Mazar - (2 on day 33, 1 on day 26)
• 5gallon pots, BioBizz organic soil/nutes

Problem:

• I planted 3 seeds of same variety.
• I'm doing soil/nutrient comparisons between them. So, their medium is slightly different.
• One of the phenos has shown some damaged on bigger/older leaves since day 1.
  
  

Is there anything I can/should do about it? Spots are getting brown (like rust).



But overall plants are fine! Others also show a bit of it, but noticeably less. It definitely seems something on this variety.

New growth looks good.
No big deal on the old leaves.