Is It Legal For A Landlord To Raise Your Rent By $300 With Less Than 3 Weeks Notice?

I’m in New Hampshire. Our landlord owns all the houses on a private street and there’s ~6 houses altogether. They’re all 1-2 bedroom houses that were originally camp lodges ~100 years ago. Then different extensions were built on them to add kitchens/extra bedrooms, etc.

Our landlord had a vacancy in one of the houses and decided to put it up for rent at a much higher cost than what we all were originally paying. And someone signed the lease to pay that price. Now they’ve decided that since they were able to get that much for that place, they’re going to up all of our rent by $300.

They already raised our rent by $100 last year for increased COL. That’s understandable. But we’ve all been told, that by the first of next month (so around three weeks from now), we all have to magically pull another $300 to our collective butts. Also, there’s no utilities included in our rent.

The other issue with this is that they also don’t want to do anything to update or repair anything and if something gets massively messed up, it takes months for it to get repaired. For example it took around a year and a half to get the some of the windows replaced because they were so old and warped you could only open 1 out of 5 windows.

There’s holes in the roof throughout the house and everything smells like mold. There’s just a whole list of things that are wrong with each and every house that they don’t want to repair, replace or update.

So basically, is it legal to raise the rent that much and give us all less than three weeks notice to magically come up with another $300 every month for our rent? Especially when none of it is put back into maintaining any of our houses or properties?

Edit: forgot to mention: we originally signed a year lease when we first moved here in January of 2020. After that, there was nothing signed and the landlord said it was a “month to month”. But they’re trying to raise the rent by another $300 with less than 3 weeks notice.

Also, not sure if it’s important but we do have the receipts for every single months rent that was directly paid into the landlord’s bank account. It’s notated on the receipts directly from the bank that it’s a rent payment and has our name on it, so the landlord can’t try to say at any point that there’s no proof that we’ve been living here without paying or anything like that.