I have just scanned hundreds of images of whites frogs and can not see anything remotely looking like that.
Quick scans of illness suggest edema from kidney failure with humane euthanasia being recommended action.
A picture from the front would make it clearer but I don't think it is a whites but a related species, White lipped treefrog (L. infrafrenata).
Edema can be brought on by a huge number of things, unclean living conditions, dirty water, vitamin toxicity, nearly all signs of very poor husbandry.
If you truly bought this and 3 others looking the same from a pet store you need to name that store here and right now!
I've seen similar symptoms in some other taxa which in general were attributed conditions that prevented or disrupted the ability of the frog to osmoregulate correctly.
However I have to say that anyone who would post a frog like that for sale and make the claim that it is really cool, should not be involved in selling animals in any way.
some comments
Ed
