Lately my LO (11 weeks) won't take expressed milk if it's more than a day old. Could my milk go bad that fast? This hasn't been a problem for the past 2 months, but now all of the sudden she'll refuse to take any EBM unless it's from the latest pumping session. What could be causing this? I'm getting nervous because she's going to daycare in a few weeks and don't want this to be a problem.