Organic First Grow HSc Blueberry Muffin

Week 3 of flower brings the first real deficiencies to the plants. I still water around 1,5l ever 3-4 days. Ordered some Advanced Nutrition Basic fertilizer to hopefully give them some much needed food. Number 2 has already grown the biggest buds and has a lush green canopy. Healthiest plant of them all. Number 1 seems to be really hungry as all leafs begin to yellow. Is this an early fade or just depleted soil? She will be my testrun for the AN Fertilizer. Number 3 is the slowest of them all , but also begins to get a lighter green canopy. Update 4 days later: Didn’t water for 7 days now and they seem to have some left in these pots. So definitely overwatered them the last 3-4 weeks. Will dial it back and continue with 1,5-2 liters per 7 days. Measured pH of my 24 hour standing water and it came out as 8 . Will use Citric acid to lower it to around 6,0 before watering.