First Outdoor Grow (Ontario)!

Sorry for the late upload, i've been super busy with exams. I bought a new Mars Hydro TSW 2000 which I hope helps. This week has been a rough though, I started nutes at 1/4- 1/2 the recommend amount and thought all was okay until I checked on them a few days later and some of there leaves were starting to die! I felt the soil and it was extremely dry so I don't know if they were just thirsty but I stopped all nutrients of course until I can figure out what killing them. Im feeding them tap water with a splash of lime juice to bring the pH down closer to 6 until my digital pH meter come in later this week and I can figure out how to reintroduce nutes. I hope I didn't cause too much damage to my plants. Im also waiting for my "CALiMAGic" to come in so hopefully il be able to introduce that to them soon. As you can tell from the photos they growing well however I don't know when I should transplant them or start topping them or even start LST? Does anyone have any experience with Mars Hydro? Is my light too close/ too far? This is my first grow so any help/ comments would be greatly appreciated! 🙏