Yellow Spots on my R2 leaves

Strain - R2
Method - Soil Pro Mix VPW 30
Vessel - pot
pH - 6.5
EC - 20-20-20 So 8.7 phosphorus 16.7 potassium … can’t seem to figure out the Nitrogen right now
Started indoor with T5 light outdoor since full moon of June which was around June 21st (late this year)
Temp on average 25°C daytime and 16°C night
My ventilation is the wind but during early indoor growth oscillating fan to promote hardening of plants
Co2 None
Average humidity 70%

I have yellow spots on the leaves of one of my plants as a beginner I’ve never encountered this problem I’ve taken the precaution of isolating it from the rest and am a bit overwhelmed with all the information online. Could you help me pls. So far I’ve come up with Septoria or Nutrient deficiency since its later in veg growth I’m not sure if it would be Nitrogen or Phosphorus.

Your ph seems a little high for promix, they recommend 5.8-6.2. Seems right at about 6 will do pretty good for most. Do you have an actual ec or ppm reading of your solution?

20-20-20 is the ratio of nitrogen to phosphorus to potassium. So that should be 20N-20P-20K, not sure where the 8.7 and 16.7 come from?

Looks like chemical or splash damage.

That was my first thought but then it spreads to other leaves