I don't know about the yellowing but when leaves go yellow it is often a sign of too much light. I have the 'finicky' grande type and I have only had it for about a month but so far so good for me. I have noticed that the new growth is putting out new roots and the leaves are growing. I don't have mine in the windowsill but about four feet away and in a semi shaded location. I grow mine in bark mainly with a bit of moss for moisture. I hope that yours makes it as they are truly lovely plants. Good luck.