RQS Euphoria - Micro Grow 63W/100W Run 4

It’s the end of the first week of flowering. Some LST here and there, nothing serious. I changed the LED bulbs 3 days into flowering to the LED strips. Let me explain my reasoning: In my 3 previous runs, I’ve experienced some serious stretching, even though I used the 6500K light bulbs the first 3 weeks of flower, from 250% to 480% stretch (ouch). I’ve come to believe that the stretch is mainly due lack of light. Here’s some math (correct me if I am wrong). The 6500K bulbs produce 6.330 lumen on a 0.2109 m² (2.27 sq ft) area, giving me 30.000 lux and according to Grow Weed Easy Lux level quick guide that’s good enough for veg, but it’s just not even above the minimum required for flowering (35.000 lux minimum required for flower). The LED strips instead produce 21.000 lumen, which will amount to 99.500 lux which, assuming I understand this correctly, is above the saturation point of the plant without CO2. I hope I'm not talking out of my ass here. So, even though I’m using 2700K light during the stretch, I hope for less stretch than in my previous runs. I’ve upped the feeding to 1.9 EC and still there are some irregular yellowing on lower leaves, most probably potassium deficiency on early stages, so I’ll be upping be adding bloom next feed.