RQS Amnesia Autoflower

After preparing the coco with 2l of water, using 4ml canna coco A+B per Litre and watering the 3 plants each day with a total of 1l Water, using 2ml of Canna A+B per Litre (ca. 0.33 for each plant), I got a run off of 2000ppm in the first week. I was not sure if this was caused by the Canna A+B, but I was alarmed and stopped the feeding in the next 4 days and only watered the plants with destilled water and Rhyzotonic. Due to this, the ppm of the run off got slightly lower: 1500 at one plant, 1000 at another. My current problem is, that compared to other plants of the same strain in week 2, they are looking super small. Why is that? Any predictions?