Purple spots on young broccoli leaves?

Question:I got these 2 broccoli plants from a friend. To my knowledge they are calabrese. After a few weeks I noticed that I was getting purple spots on the new leaves - this happened only on one plant but now I've spotted it on the other one. I have checked out various books I have and google, etc, but havent found anything listed. The leaves look healthy enough. Does anyone know if this is a bad sign? I keep seeing things in books where it says if you see this burn your crop and dont grow anything there for a year etc. It may be I've got purple sprouting broccoli but nothing I've seen suggests the leaves go purple too. Anyone hit this before?

Answers:
its fine