HELP! Firstimer

[Firstimer86]

Bubblegum plus photoperiod
soil outdoor / greenhouse
40lt pot
Universal feed 2lt water every 3/4 days
6/7 weeks left of flower
Day temp 15 /20
night temp10/15
Problem
Light browning on stems pictures included has any body seen this problem befor I am struggling to find info
everything above the browning is still real healthy
Noticed browning 10 days ago

[Qwertywill]

The stems will turn brown and hard over time, mainly issues will arise in the leaves

You should be fine.