Should I keep going for 13 weeks

Why exactly have you chosen 13 weeks? Is it some sort of superstition? Seriously though, some of your plants look ready, some nearly ready and some another week or two. Each plant will be ready in its own time and not all your plants will be ready together. Leaving cannabis to become over ripe results in heavy sleepy type of stone due to the THC breaking down into CBD and CBN. If you prefer a more up style of high, harvest your plants when the pistils have all but browned off completely, with still some of the very last pistils showing some white. Leave them to be completely browned and withered if you prefer the heavy sleepy stone. I personally prefer to judge my plants maturity/ripeness by judging pistil condition, as this better reflects the plants overall health. Waiting until all the pistils have withered completely means the plant is close to death, hence the THC breaking down, due to an almost stagnant metabolism. Also, some strains will never develop amber trichomes for whatever reason and waiting for trichomes to turn amber well beyond the peak stage can result in inferior cannabis. Judging by trichome colour is easy for newbies to see, but is not the definitive method. I have had plants with 30-40% amber trichomes after only 4 weeks in flower, about 4-5 weeks before maturity. Fortunately I didn't do what the internet told me and harvested when the plant had 20-25% amber trichomes! So, it is up to you and which type of stone/high you prefer. Pick a bit earlier for clear up style of high or leave a bit longer for heavy sleepy style of stone. All in all, you need to harvest the plants individually when they are ready to your liking and not leave harvest to dates on a calendar. Hope this helps,... Organoman.