So I've started 2 of Nirvana's Blackberry seeds, germed them fine and they sprouted fine, but something odd is happening with the stems as of the past two days. The stems themselves are purple, but two days ago they appeared to shrink in the middle and turn a real light green, almost transparent. I killed one becuase it was falling over at that spot but the other is doing it now too, not really sure what to do or whats wrong. I looked through the plant problems sections but I didn't find anything that really described my problem at all, and from what I searched I coudln't find anything in 5 or 6 pages. Anyone have any solutions, diagnosis or anything would be great thanks.