It's possible, particularly the suggested asbestos link.
But Carry John did very little work at Television Centre after leaving Who, though she did do a lot for Granada, whose studios were built in the same era so presumably had the same asbestos problem. Arguing against that, you'd expect there to be a lot of casualties among the Corrie cast as a result, and that's not the case.
Add in on that: there's a trend for women to either live long, into their 90s, or die a little early, in their 60s (average lifespan is only an average), whereas men tend to die closer to the average lifespan.
A rogue element might be the Fuller's Earth used in FX explosions on Who: it's been blamed for the cancer deaths of the Dad's Army cast (who were already elderly, but who went down to cancer more than averages would suggest, and had waded their way through massive FX explosions for the end title sequence).
Still, it's probably just a sad set of coincidences. And very probably the smoking.