Some of my lovely sweet smelling home-made (hand made) hay has gone musty

. It was stored in a shed for a couple of months - I've used this shed to store hay in before but maybe not for quite so long and maybe usually there is more ventilation with me going in and out of it (it's an ordinary garden shed).
It's still green and hasn't changed colour at all. The smell is all the way through the bales (i.e. inside and out) but there are no dark or mouldy patches anywhere on them.
Is there any way to revive these bales? (Currently the sheep are turning their noses up at it

.) or must I consign these to the compost heap?