Auto pots - second grow

So this is only my second grow. 4 x Pure Ak from female seeds and I am growing this strain as I have read its fairly easy to grow and its good for chronic pain. I love learning new things by making mistakes and this journal will be no exception. So my first grow I soley used a Mars hydro 300 on one plant. This grow I started 2 plants but got worried about killing the plants and started another pair to increase my odds. After coming to my senses I realised that 4 plants under that one light was never really going to get the job done so I bought a Viparspectre 650 to supplement the mars hydro. With regards to germinating the seeds I used the paper towel method followed by red paper cups. Once the leaves reached the edges of the cups I then transferred them. Due to personal circumstances on my last grow I also purchased the 4 auto pot set with the 47 litre tank just in case I had to go away for a few days. After 4 weeks I can say that the system was easy to set up though I was missing 2 root control matts with the delivery. Within the pots I used the matts, an inch of ph'd clay balls along with biobizz light mix. Once I put the plants into the autopots I poured 3 litres of ph'd 5.8 water into each pot. A note. The mistake I made was I did not realise how far the biobizz would fall within the pot so all my pots are only 3/4 full of biobizz and Clay pebbles. After 14 days which was reccomended by auto pots I filled the res with just ph'd 5.8 water. I did not use any nutes as I read lost growers over feed thier plants and the plants can still do well with minamal nutes ( more on this later) So after checking the res over the next couple of days I noticed that the res was a ph of 5.8 but the trays all had ph's of 6.3 - 6.7. I have no idea if this is a problem but the girls were still growing nicley. The next thing I noticed was the roots were growing in the trays towards the aquavalves. The roots looked healthy but I did not want them clogging the valves and after some research purchased 4 auto pot socks whih fitted nicley. The next potential issue was the two plants on the left started getting brown spots. After more research I am guessing nute deficiency becuse one I hadn't fed them any nutes and looking at other pure ak diary's they are nute Hungry. The only nutes I had in the house was this formulex growth technology which is pretty weak but good for seedling so I started putting thatin res slowly increasing it to 700 ppm over a couplel of days. If its not nute deficiency could someone let me know please? Currently have shogan a&b on order as it seems tryed and tested on this website. After researching I then decided to top 3 of the plants with sterile scissors. So the res has been feeding into the girls for a week now. Whilst I have had good growth on the older girls. I'm wondering how much I hindered the growth by not feeding them nutriants. Thats everything for now and I will keep updating with my mistakes =)