How far down are the ears drooping? Does it look like they're actually lops, or are the ears just drooping half-mast or so, like they're too heavy to hold up?
During warm weather, I've had bunnies whose ears grew so long, so fast, that they did not have great ear control, and the ears tipped forward/sideways for a while. I've found this happens more often with my larger meat breeds like NZ and Champagne D'Argents, and I've seen it quite frequently in my friend's Flemish, but I've had it happen with Satins, too. It resolves itself, sometimes coming and going from one day to the next, and the warm-weather bunnies always eventually grow into their ears.
The other issue I've seen with drooping ears is a Vitamin E deficiency, but in that case the ears drooped over at the tips, kind of like a collie. It affected the entire litter, but I suppose that if it was a borderline deficiency you might only see it in the smallest, least competitive kits. This was during a period when I and fellow breeders had one reproductive issue after another, and we discovered it was a problem with the feed. Doesn't sound like that's what's going with your rabbits, though.
As far as the dragging back leg, that can happen when a kit gets a toenail or toe stuck in the cage wire bottom and wrenches it. If it's no longer a problem, it doesn't seem like it would be due to a progressive disease affecting neurological health, like meningitis. I've not dealt with meningitis but I think that usually comes with other obvious health issues like respiratory and coordination issues.
If it was me, if they're acting normally otherwise, I'd probably leave them where they are and watch, taking care to be meticulous about providing plentiful clean water. I'd probably also put up solid barriers between the cage they're in and others, just in case. If they're contagious they've probably already shared whatever it is with the mother; and if they're somehow compromised, moving them will stress them further.
Can you post pictures?
