You were right with your answer, the icing was too stiff. The cake still looks beautiful tho!
Cat
Either the buttercream was too stiff or you were piping the petals too slowly and turning the nail too quickly. I know that's what my problem is, but I just can't seem to get the hang of it yet. One time I got a rose to come out with no jagged edges (while every other one, before and after, from that batch DID have those edges) by just really going for it and piping the petals with confidence which meant squeezing a lot more out per petal. It looked pretty bad with the sort of imperfect petal arrangement, but at least the edges weren't jagged!
When mine do this, i touch the edges lightly and bend them under some, cause i dont want to redo 
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