Yeah, I agree with everyone else - very normal.
Good luck trying to stop them
Mum should be getting her full ration now (her 3-4lbs, plus half a pound for each piglet) and depending on how much the little darlings are eating you might need to up it a bit more if she starts to lose condition.
Once they get to 3-4 weeks you could start to put some out for them too. A great, easy & cheap piglet trough can be made from a bit of guttering screwed onto a couple of wooden blocks - and it's very funny to watch them eat a bit then jump up into it and walk along hoovering up the extra
Grapes are what I've found to be Kune piglets favourite treat, though they'll eat any fruit quite happily (and hand feeding them makes it very easy to get them nice and tame and socialised
)
Karen