Moby Dick XXL Auto Outdoor Soil

Start my diary as I have some issues and looking for help. I germinated 5 seeds straight into coco pellets seedling starter kit, that comes with a 3.5cm pot. Two of them popped out right away, two more just after and the final one at day 5. I gave them some sun from behind the window and sprayed with ph 6.5 water. Then i noticed the tap root appear on the biggest one so i transferred to their final 15l fabric pots. The soil was a mix of local organic compost 1/3, 1/3 coco coir and 1/3 perlite/guano organic soil mix, also lined the bottoms with clay balls around 1 inch. I watered them until run off a couple of days before transplanting the biodegradable pots directly into the middle. For the first 10-12 days I gave them only ph 6.5 tap water (left for over 24h + lemon juice to bring the ph down or vinegar). Then around day 12 they weren´t growing much and was told at the local grow shop to start adding AN Grow Bloom Micro at 1ml/l plus ATA Rooffast at 1ml/l. I gave them all 0.5 of each AN fert and 1ml of root fast with 1l of ph6.5 water, they were fine and then again after they dried out which seemed very quick (it can hit 30+ here in the day) i gave them the same, then i noticed 3 out of the 5 stopped growing and the biggest two did fine, I have sinced allowed them to recover only giving them ph 6.5 water for the last week when fully dried out, but they don´t seem to have recovered...the other two "big" ones are now at day 20 and still seem really small to me...any tips advice help would be greatly appreciated...