I have had also snowdrops coming up yellow if there had been too much mulch on top of them.
'Jaquenetta' and 'Cordelia' have been very similar for me, only this year some markings in 'Cordelia' are as they should be. Also 'Jaquenetta' comes up always a bit earlier than 'Cordelia' and J becomes taller when the flowering advances.
'Cordelia' came up this year only a couple of days behind J, both are now the among the earliest snowdrops this year, because they grow in the warmest spot. About half of my snowdrops are still just peaking from the ground and many don't show yet. This has been a very cold winter for them, so we'll see later if I have lost any.