sorry for the late reply - i have been away.
they live in the outhouse but have a catflap leading out into their run, which is on the patio. I have grown some grass in tubs (everyone thinks i'm mad!!!) for them, which are now in the run so it might be that I suppose, although the tubs have been oin there a while, before they cut back.
However, they seems to be pretty much back to normal now.
And like you, I have tried every diddferent type of hay going, pet shops, farm shops, online - I think Stella is just fussy!!