Under a year....your builder should be taking the lead on this for you. Naturally, he will be getting his plumbing sub involved. Bradford White has a much better reputation than this. We can't tell from your description...( photos please!) but no way a tank rusted out or failed in a year. Almost surely caused by some kind of install error. Has a plumbing contractor, or a BW rep...looked at this and told you why it has failed? or why they won't replace it????
We don't recommend the Whirlpools from Lowes, but on an electric, it is probably OK. Be careful on the legal front.....you must exhaust ALL your administrative remedies or a judge may not rule in your favor. Again....this should be in the builders lap.