Hey E.,
Just keep your strength up with lots of great high quality protein and your nursing child will be just fine and get back on track with the baby food in good time. Babies don't over eat like adults will, so they eat when their bodies need it, period. As for the three year old, I know my girls do that same thing. Sometimes up to two weeks or so before they get back on track. My guess is, she just isn't hungry, or ready to eat. Just keep offering high quality protein ridden snacks and other healthy choices continually, and in time she will bite. We always have food sitting around and such on the counter ie. strawberries sitting in a bowl/ which is sitting in a bowl of ice ( which eventually becomes cool water) ... Slices of oranges and other just snacks.... Toddlers eat randomly and here and there. If it is there, and without much effort to get to, they will eat. Above all else. Seek the Holy Spirit's leading on what to provide for her that she WILL want, and that will provide the best sense of the answer on this. God can make a way where there IS no other way. That is the Holy Spirit's job anyways, So ASK, and the answer will indeed come.
Much Love ! Be Blessed. Your children are so very lucky to have a Mom who covers their concerns with prayer:o) !