Alfalfa v. Timothy

Okay, all my piggies are under 6 months of age (1 month, 2 months, 4 months, and 5 months). I started out giving them unlimited timothy, and then a couple handfuls of alfalfa a day, because I read somewhere (can't remember now) that they should be givne unlimited timothy and then just some alfalfa. Then, I found out that I should be giving them only unlimited alfalfa, so I gradually changed them to that - I mixed in timothy with the alfalfa, and decreased the amounts until it was only alfalfa.

They're still doing what they did then - Only eating the stalks, not the leaves. I've been worried they're not eating enough hay/whatever, so I threw in a big ol' clump of timothy. My piggies, who usually run in fear of their lives from my hand, apparently saw/smelled the timothy, followed my hand over to the hay tray, and promptly began munching on it as soon as my hand was gone. They're popcorning all over the place now, and STILL munching on their big ol' pile of timothy.

It seems kind of strange to me, because it was my understanding that animals will go for the alfalfa before the timothy - it is supposed to be used as kind of an eating/hunger stimulant in some cases, right?

Should I just change to give them all timothy? I'm REALLY worried they're not getting enough fiber. They get lots of veggies, and eat all of their pellets, but... yeah. =P

Could it be that they weren't wearing their molars down sufficiently, so they only ate the hard stalks isntead of the soft leaves? They've been chewing on their tube and wooden hidey house...

I want my piggies to be healthy and grow up to be big and strong, so I don't know what to do! >.<