Security Deposit question?

i recently moved out of an apartment that I shared with 3 people. Months ago the drain plug in the bathroom broke so the lever was naturally in the position so the tub wouldn't drain. We told the landlord via a voice mail he says he did not receive and it kind of became a part of our life so we forgot about it and just got used to rigging it so it would drain without us holding it down. We realized it could have been an issue right before we moved out and naturally it was. The landlord is trying to charge us for the cost of the repair from our security deposit. With the knowledge that we should have taken care of it sooner, does he have any right to do this? It did not affect his ability to rent the house (he received full payment for the month of June, the month after we moved out) and the piece broke through no fault of our own (it rusted through, something we clearly could not cause). Any incite you could give me would be fantastic. Thanks!