My condolences to the person in your family with Rickets.
If it makes you feel any better, correlation does not equal causation. Just because you bought a new laptop doesn't mean you are responsible for one of your family members suddenly having Rickets (unless the money spent was meant for a treatment procedure or something).
There's no way to predict this sort of thing unless you just happen to notice all the external factors beforehand, it's not your fault.
Is it the air quality or is the problem that they too sit indoors using laptops they don't need rather than going out to play as the children of yesterday did?
Sounds like a very random phone call either way...
That is so close to being a boomer moment, if it weren't for the implication that we're no different.
Additionally, going out to play in the middle of the industrial side of China probably isn't a very good idea.