Hello again.
How long have these plants been in this soil ? It's a preloaded soil meant to sustain the plant for quite some time.
It's N-P-K = 14-16-18. Quite high in Nitrogen, Phosphorus and Potassium.
The reason I'm asking is. If you take a look at the tips of the leaves in the first picture you posted. A lot of the leaf tips are curled under. This is a sign of very high soil nitrogen content and the plant is not happy about it.
The liquid fertilizer 8-3-7
1 L of this stuff contains 80,000 PPM N
30,000 PPM P
70,000 ppm K
If you put 5ml = 1 teaspoon in 1 liter of water you dilute it 200 X
5ml X 200 = 1 Liter
400 PPM Nitrogen 400 PPM is at least double the nitrogen content you should be feeding!
150 PPM Phosphorus
350 PPM Potassium
So Dilute it. 1 teaspoon - 5ml in 2 liters water.
200 PPM Nitrogen 200PPM Nitrogen is still just a little on the high side. It's ok for a plant twice this size.
75 PPM Phosphorus
175 PPM Potassium
Lets look at 1 Teaspoon = 5ML in 3 Liters water.
133 PPM Nitrogen - I'd say that this would be the correct dilution for this plant.
50 PPM Phosphorus
116 PPM Potassium
***** You must first take into consideration that the plant is in a preloaded soil.
Only after the plant has used up the nutrients in the soil, is it safe to use the liquid fertilizer dilutions suggested above!
Basically it's likely sitting in hot soil.
Stop feeding. Do a nitrogen content in the soil test and see where it's at.
When the plant has used up the available Nitrogen in the soil pick up feeding.
5 ML in 3 Liters water threw Veg.