Hi
My first litter of puppies have been gaining between 5-10% a day for first 10 days ( mostly nearer 5 than 10, she's a small dog and had 6 puppies. First Q, does this sound ok?
Second Q, they are now 12 days old and weight gain is slowing down, to 2-4% last two days. Does this sound ok?
Third Q, does % weight gain begin to naturally slow down and if so to what sort of level.
Thanks. I'd really appreciate your experienced opinion.

As long as they are all gaining, there is nothing to worry about. Even the odd day where they haven't gained or dropped a couple of grams is normal.

I realise I may get my head bitten off for saying this, but:

I would suggest that you try "helping" a little.  By that I mean watching to see if all the puppies are getting equal nourishment, and by encouraging frequent feedings.  I have found that I can further weight gain by putting the puppies on Mum to nurse a little more often than they might otherwise do.  Especially as the puppies get older and sleep longer between nursing.  Yes, yes, I suppose that is "interfering".  I can only say one thing:  it works.  When everybody is steadily gaining again, you don't need to continue doing this.

As long as they are all gaining I wouldn't worry too much. If one or two aren't gaining anything like as much as the others, you can try plugging them onto a back teat for better milk flow, but if they are all much the same it's probably fine. :-)