x5
Not to sound like an a - hole, but yea they Kinda warned you.
Also, as mentioned above, most warranties I have seen are for 15 days, and from time to time I see a 30 day one. So it's not their obligation to refund the money or do an 'exchange'. If they said they'll break a deal with you be thankful and accept it (a 50% would be more than awesome in this case).
But, as a vendor, I think they failed, selling a 'sick' snake.
Just give it a go, Hope you can get a new healthy one for a great price.