OK, you go ahead and grow your plants in soil in pH 6.0 and I'll see you when you come back here asking why you have a Cal/Mag issue. Sorry, I don't get all my information "off the back of a nutrient bottle". Here's a good chart to show you why it would be better to go a little OVER 6.5 rather than UNDER. Although 6.5 is the sweet spot.
I don't know where you got that chart but I don't trust it, when your soil's PH is acidic,"(6.5)-(7)", you not only have problems with your nutrient uptake but you can have problems with your leaves burning if you have a fan on low blowing on them,especially if your RH is 40-50 percent which is optimal. I'd rather trust every company saying that the PH should be between 5.5-6.5,than some hokie graph you got off the internet. Cal/mag isn't the issue it's the solution,the issue would be; calcium,mag.,potassium,zinc,iron deficiencies which isn't a problem with ph around 6 because i've grown with it numerous times and i'm not the only one that seconds this. If your not using RO, chances are your not going to need cal/mag because your water probably already contains between 150-300 ppm of these substances, Come back when you know the truth about PH and nutrients. Oregon The Chronic State.
I have looked at numerous charts, guides, and web sites about growing marijuana in soil and they ALL say the pH needs to be between 6.5 -7.0. I don't know where you are getting your information, but it doesn't agree with the general concencus. If you can grow in acidic soil maybe you have a strain that is tolerant or you are doing something else to offset the soil's acidity. Maybe you're just lucky. It really doesn't matter. Most people won't have good luck growing in pH 6.0 soil, so I'm going to continue to tell them to use the correct pH of 6.5-6.8.