Given the proximity in time between the quitclaim deed and your mother's passing, you have an argument that she retained a life estate (by implication if not expressed in the deed) with you and your siblings receiving a remainder interest.

However, you should consult with a local tax professional and/or legal counsel considering the dollar amounts. If (when) you do, mention an "implied life estate" per Section 20.2036-1.

https://www.law.cornell.edu/cfr/text/26/20.2036-1

The foregoing will work toward your advantage in a major way in terms of taxation.