Alot of post about this, all we can do is go by what you see, the calyx and the time of flower. In order to really tell you if they are ready we would need at least a 60 times magnification of the trichs 100x would be better. To be honest they look very close but thats about i could tell you other than you have done a great job on growing them. GOOD LUCK AND HAPPY SMOKING
I'm guessing that they'd need as much as 3 weeks longer. Here's a good guide for when to harvest. Don't harvest too early, it's worth the wait. When is the Best Time to Harvest Marijuana Buds? | Grow Weed Easy