Something is only worth what a buyer is willing to pay for at the current moment. Right now, the buyers are saying the house is worth $1.15M. You can reject those offers and wait to see if there will be better offer in the future. No one can tell the future, so it’s your decision. Buyer don’t have to give reason as to why they offer a certain price. Buyers don’t have to give reason when offering above or at asking, so why should they give reason for offering below asking other than the fact that it’s what they think the house is worth.