How common are respiratory infections in tortoises?

it is pretty common and is easily treated, i would think that the fact your tortoises got sick so soon after you brought them it is a problem the store has, they do not have their set up right and if they are keeping a lot of tortoises together then something like this will spread like wildfire through the tortoises, it does not sound like the store is caring for the tortoises very well, the problems with Greek tortoises is they are quite sensitive to change, and if she was not at full strength when you got her the stress of moving environments and the worms can make her stressed, i don't think it is anything you have done just bad husbandry at the store, respiratory infections are quite common and are usually the result of incorrect temps and enclosures and a poor diet, it is lucky you have obviously done your research on tortoises and picked it up quick, your tortoises are the lucky ones, if you intend to get any more tortoises i would find another place to get them the store where you get them don't sound like they know how to care for tortoises very well, the good thing is your tortoises are fit now keep up the good work best of luck