When you say that they don't to "anything" but lay about in holes they've dug, do you mean that literally-- that they're not running about, scratching everywhere, eating and drinking well, making noise, eating bugs? If so, it sounds like they may be sick; I'd post in the "chicken illness" part of the forum for advice there.
If they are healthy (running, scratching, eating, drinking, etc)-- let's see... 40 sq ft for 5 birds is on the small side, but not so small that it should stress them to the point of not laying. Five different breeds means that it's not just a late-developing breed or bad gene pool or something. By six months, you'd have noticed if they were all roosters, I think... So let's ask the big question: what are you feeding them? To get eggs, you'll need to be giving them plenty of feed that is specifically labeled "for layers" that will have the right ratio of nutrients (especially protein) for egg-laying. If you've been feeding them layer feed, try waiting a few more weeks (b/c six months is not THAT late) then switching brands-- poke around here, there's tons of recommendations.
Good luck!