People, don't be that alarmist.
Lisa isn't skinny. She may have lost some weight from the times when that first picture was taken, indeed, but she is perfectly fit on her size by now.
I have met her personally not only once, but twice, I have even hugged her, and I'd say I'm quite thiner than her, me being still ok and not being one of the thiniest persons around at all, so she's perfectly and very well looking by now too, I must say.
So don't worry.

Pictures are never reliable 100%
Anyway, even if being on tour may not be the best thing for their health, but they don't come on tour that much so there is not a lot to worry by now.