hey there, the slightly purple stems come from small stress at the root level, also you can see the slight downwards curling on the leafs. What you need to do is just water a little bit slower maybe 6-12 hours less often to make sure you respect a strick wet dry cycle. Hopefully this will fix it... if the problem gets worse you'll need something to break down the problem roots. Great work so far actually ! Hope this helps ! 🚀