Hello AF growers I am looking for some help here. Below I have pictures of my first grow ever(I have a journal of it as well). The reason I am posting here is that the bottom of my stem had gotten a "woody" type texture/look at the base of it. It didn't seem to hurt my first grow at all, but my friend that had a lot more plants actually lost 2-3 plants because of snappage from the stem problem(same situation as mine). Now, onto my 2nd grow ever. I'm about in 2 weeks on the system and now my new plant is starting to get white spots on the bottom of the stem--that I can rub off--and now the stem is starting to look a bit woody again and looks thinner than the rest of the plant which actually looks thick now(no pictures sorry just from the first grow but i can take one later). Here's the pictures from the first grow stem problem:
Please, if you guys have any thoughts give me some insight.

