It's totally up to the plant. I'm probably gonna chop that GG4 next weekend which would make it 9 and 1/2 weeks. As a general rule I usually estimate they take about 2 weeks longer but sometimes it's way more.
I meant about a month after the first pics which you said were the beginning of week 7. I might've even went a little more than a month. This is 7 weeks for my GG4 but I'm giving them another 2-3 weeks. I like to let the calyxes swell up first.
1. He's doing organics so runoff isn't a great idea.
2. Runoff also isn't a good way to measure soil pH.
3. Vinegar is a milder acid compared to phosphoric acid which is what most pH down is so it's not going to hurt the microbes unless you use a lot. I don't think phosphoric acid would do much...
I'd say the brown edges and tips is probably the soil mixture. I don't know anything about the 2 soils you mixed but that would be my first guess. It's not Mg deficiency. I'd do plain water for now and see if they get better. The soil might just need some time to balance out. EWC or an EWC tea...