@MattyBear you can use lemon juice in a pinch and it works fine.
I’m running a variety of strains and my nutes are always between 5.5 and 5.8. I defy you to even find one nute burned tip on one of my plants. Ph outside that range and you risk problems. At the very least stunted growth.
I would strongly suggest that you keep your tds values in veg around 600 to 700 ppm at 5.5 to 5.8 ph and if you are using RO water or low hardness (under 200 ppm) to add cal mag.
If you follow that you’d better stand back because they are monsters.