Plants growing purple ish stems

[aaronweiner2016]

My plants are growing purple ish red ish stems. What could my problem be if there is one?

 

[detroitjoe]

your a lousy videographer. next time, slow down .

plants look great but over crowded.
appears that the stems on the leaves are growing faster than they should because of the stretch for light.
overall, they look great. open them up a little