Well thank you all! And in reply ;
Yes, we've had plenty of grass this year - no concerns there.
Udder shows no signs of mastitis, no soreness etc. There's definitely milk there as we've turned her over and checked.
Other lambs doing fine. It's just these two.
From the advice you have all kindly provided I will keep them close to home, give them a dose of vits (if they can be caught -I will have to think of some fiendish plan to get them in the pen) and keep feeding creep in slowly increasing amounts. And then see how it goes.
I don't breed my sheep for the meat market - they are purely for their fleeces so it's not important to 'fatten' them, I would just like to see them growing properly.
Thank you all again. And hello Anke! Long time since we've chatted. Hope all well with you and yours.