I don't think those are the right ferns. From the look of the leaves, the appear to be a different type of fern. I've been picking fiddleheads for about 30 years so I do know what I'm talking about. There are so many different types of ferns and some of them aren't safe to eat. Actually what is interesting is that quite a few of the pictures on the link you posted are not proper fiddleheads at all - they may be called fiddleheads from the shape of the sprout, but they are definitely not all edible fiddleheads. Sorry.