This is for anyone that can educate me on this my ...

The very top bud on your purple plant is getting mild light stress, you could remove this one bud as a test smoke. But the rest of the plant still has a couple of weeks left from what I can see 👍🌱

Hey ez gro, there is only one determining factor in whether you should harvest part of your plant and let the lower parts mature. If you are running a 100% organic grow that doesn't use any chemical fertilizer then it is fine to harvest the tops and let the rest mature. But if you are running any chemical fertilizers then it is best to flush the entire plant and harvest. I don't see your nutrients listed but I am pretty sure the calmag you are using contains chemical fertilizers. So in this case I would monitor the trichomes around the middle of the plant and flush accordingly to determine your harvest time. Unfortunately on most grows you will have some lower buds that don't mature and those are great for making hash or edibles. If you cut buds off that are not flushed of chemicals then it will affect the flavor and ultimate experience of the buds you put so much effort into growing. So it is really a balance of do you want the most potent top buds or the best balance of your entire crop. Hope this helps.