I noticed some leaves and stems getting red/purple...

Hey there the plant appears healthy and you're so close to completion so i wouldn't worry too much about the colored stems. However for the future grows they can change color for many reasons, whether genetics (like in my case), phosphorus deficiency but usually that happens when your ph is too low rather than higher like yours at 7. But also a common cause is actually a magnesium deficiency, however that would also be marked by slowed growth and sometimes leaf changes fading etc. Great job with the grow and happy harvesting. ✌️

Are you sure it is a deficiency? The plants often change colour when getting ready for harvest, was the same with me! Check out on my finished grow. They turned nice and purple but I thougt it was normal. Smoke was excellent tho :)