Hi Susan
I would not worry about the leaf yellowing, normal in winter, they should green up in March. Even if there is a little mould, which I have seen before on onion sets too.
For sure it is not white rot but it can sometimes end up rotting sets before planting, when they are too damp in a bag I think, and your garlic is probably feeling damp… I would plant the elephant garlic if the mould is only small, odd patches but not if their whole base is mouldy – you could ask for a refund, I have done that before.