You for sure need to remove the planks and if you are lucky you might be able to save them I have the kind that have no backing so they just lift up dry out and can be relaid .Servo pro will know what has to be done and if the flooring can be saved.

When you say short period of time, what’s the time frame your talking here? its moisture from the crawspace that has actually come up through the sub flooring. it has possibly been wet for weeks. This is a new build literally finished it a couple months ago!

Who knows. You will not know for sure until the floor is up. You definitely need a moisture barrier. Is this a wood framed flooring system? Slab? Crawl space? You very well may have a serious mold issue which require the subfloor removed, especially being as that looks to be OSB.

That was not IMO the proper sub floor anyway so hopefully that will be replaced and there is a serious water proofing issue that the builder needs to deal with and ASAP

Wood framed flooring system with crawl space

Dirt floor in the crawl or concrete? Dehumidifier? Why no moisture barrier?

If this home was finished just a few months ago you are WELL inside the builder's warranty (2, 5, 10 year is standard in Canada). You will need them to come back ASAP!

Whomsoever designed/built this home (the company...not you) is in for a big repair bill. A wooden subfloor should NEVER look like that! Ever.

Get hold of your builder and get an emergency visit! While you are waiting for your Builder to show up, you can feel free to call your home insurance company to see who they work with for water/fire/mould remediation. Calling the inspector who said the house was 'move in ready' is not a bad touch either. You want as MUCH PRESSURE on the Builder as POSSIBLE. They will move faster if they know there are SEVERAL AGENCIES looking at them!

Take photos EVERY STEP of the way. If in doubt, document, document, document. You will need ALL of it to force the builder to step up and do the repairs necessary.