Deficiency - yellow leaves/spots - help needed

Hello!
Does anyone have a suspicion about what might be causing the deficiency in the plant?

Strain: Sour Diesel (Zamnesia, Feminized)
Pot size (liters): 11 liters
Cultivation area (m²): 0.16m2
Medium: Soil, Plagron Light Mix
Current veg or flower day: 36th veg
Fertilizer: Calcinit and Epsom salt to reach 80 mg/l calcium and 26 mg/l magnesium. Nothing else added.
Lighting: Sanlight Q1W, 50 watts, 60% intensity with 20cm distance.
pH/EC: pH: 6.5 EC 0.8
Air humidity: Currently 45-55%
Air temperature: 25-29°C
Soil temperature: 25-29°C
Watering: Quantity: 3.7l for an 11l pot
Watering: Frequency: every 3-5 days
- It has been regularly repotted from 0.5 to 3.5 to 5.7 to 11 liters.

Small push. Hope someone can help.

Excellent information provided.

Your plant is getting nitrogen and calcium from the calcium nitrate. It's getting magnesium and sulfur from the magnesium sulfate. Since the soil you're using is a light mix and only good for a week or two, you need to add a fertilizer to your mix, like Masterblend or something so it can get phosphorus, potassium and micronutrients like iron, boron, molybdenum, manganese, zinc, copper, etc.

You also may want to consider raising the light for more even light coverage. 20cm is pretty tight. Better to have it brighter and higher than tight and more dimmed.