topping at second node

hey guys, noob here - first post. anyway after seeing a really kickass little bushy closet setup I decided to try topping at the second node to try to really bush this plant out. Its been three days and now the stem is turning a dark purple, almost black. I figure its stress but I have a new grow area with CFLs and germinated some new seeds in there and they're all starting with purple stems too. Could be separate issues but WTF??

pics are 3 days after topping, think we'll pull through?

think the seedling stems being purple and this issue might be related? sometimes I catch the temp rising into the 80s in this new box im growing in.

are the bottoms of your leafs purple aswell?

no, and actually this one recovered very well. so well I actually made a thread I was so impressed. here she is about a week ago