Hi Gypsy, thanks for your reply.

Sweet Pea is now 3 months plus. I doubt it's due to adolescence as she only started grunting after her siblings left. Now she probably feels insecure and doesn't want to come out of her cage for runs. If I shut the cage, she'll stand outside it and look in instead of running around.

Both parents have to be lionheads in order for any babies to be double-maned, ie. they inherit one mane gene from each parent. Is that the case with your bunny?