Compared to my old pair (who hissed, played, grunted, chased me, played tag with me, etc. from the first day I brought them home) these two just seem to not act like ferrets?

They don't make noises, they don't play with me, or one another, they kind of just wander, dig at the carpet, poop, then go to sleep. They're adopted and I don't know their exact age, but they're between 2-4 years old. 

I've owned them for about 2 weeks. They played the first day I brought them home, then poof! They're just kind of... mellow. 

The female is deaf, would that be a factor? The male has no issues, however.