Ah, you have the leaf set between fingers - looked like you clipped it....
Hmm, Barney's LSD doesn't "purple" ..... Too much K somehow? K will cause that "purple" onset that you have.....Stunts the plant too....
I really don't see that a lot around here....Looks like it could use a bit more N too...
What soil is it in? Maybe the quality control on the soil took a shit on that batch.....does happen...