How bright is your light?
I've had a bunch of seedlings under a 400 watt metal halide for.. About a 6 months & they're not really 'jumping up', but they're still alive.
Soon I'm going to move them outside & see what happens.

Pot size might also be a factor- They're in little 2" pots at the moment so when I move them up to 4" ones hopefully something will happen.

They've also been getting pure rainwater all winter so we'll see what happens when they get a little fertilizer.

I guess the message is don't fret too much- your not the only one with slow growing kids.

Most of mine start out pretty slow as well. I have some that are 6 months old and less then a foot long. I don't move my seedlings up a pot size until I see roots coming from the drainage holes. I have some that will remain in a 4" pot for a year. I've had problems with too much moisture with small plants (small root systems) in big pots and it's not only passies. It's with all my plants. I'd rather have them root bound then root rot.
Karyn