3x Gorilla Haze outdoor in Germany

After a long period of darkness and rain, the weather abruptly got just perfect to grow some stuff. While the days were warm and sunny, the nights were mild with just a little rainfall on one day. The next week may bring some more rain, but the sunny days still make the majority. On plant 1 I noticed a strange detail. As you can see on the pictures, it looks like as if the skin of stem just bursted. I dont know how that could have happened, but it doesn't seem to have a negative impact for the plant. Plant 1 ~162cm Plant 2 ~161cm Plant 3 ~140cm