1st time DWC, 2nd time growing

Hey there again :)), Today, the plant completed two weeks since germination. Everything is going well so far, I got root rot on because the reservoir is transparent and there was light goes through it but I took care of it. There was delay on my package which was included the Hydroguard and Voodoo Juice. I cleaned the roots and I covered the reservoir with a towel to get rid of it till next water change so I can cover it with "Aluminum" as your answered you guys to my question last week. I was facing many issues during the 2nd week, and trying to discover & manage the environment in my tent and the reservoir. One of these issue is the leaves are getting brown spots which I think is the calcium deficiency because my pH in the first days was 5.6 - 5.8 and as I read "calcium is best absorbed by the roots in the 6.2 – 6.5 pH range", so I raised my pH now to 6. My second issue, leaves are being twisted which I think because of the light heat. My tent is too small and I'm using 300W LED and the distance between the plant and the light and I raised the distance to 26" And that's all what's going on with my plant. BTW, nutrients used for 2 gallons of water no as it said above ml/l. Thanks,