My puppies are 17 days old today, and it seems that once again with Felicia's puppies, I am going to experience a couple of the puppies suddenly not gaining properly anymore.  This is her third litter, and in the other two litters, I had two pups who stopped gaining around the second half of week three (about day 17, as now) and into the fourth week.  I had to supplement their feedings.  Meanwhile their siblings were gaining plenty.  But the two were not really interested in nursing properly and just played with the teats instead of nursing.  With the first litter, the vet found nothing wrong at all, but two had stopped nursing and their temperatures had fallen dangerously low.  I supplemented like crazy, and they got back into swing within a few days.  With the second litter I simply supplemented (without going to the vet), and they started gaining again.  Now it looks like this is going to happen this time as well with one puppy, if not two.  Does anyone have any ideas why this should occur at this age?  It is too soon to talk seriously about weaning.  They can't even stand up yet.
Felicia has plenty of milk, and just now I observed the puppy in question for over 30 minutes while he had the teat in his mouth and appeared to be eagerly nursing.  But when I put him on the scale, he had gained next to nothing, a gram or two.  He is not ill!  Quite the contrary, he is full of vigor!  Since birth until now he has been steadily gaining between 30 and 40 grams a day, which is just fine.  But from yesterday to today he gained only 4 grams and does not seem to be gaining anything today either, even though he nurses.
The only thing which occurs to me is that this phenomenon has taken place each time (in Felicia's previous two litters and again now) more or less around the time of the first worming of the puppies.   The first time it happened, I attributed it to Panacur and have never used the product since.  Yesterday they had their first dose of Welpan.  I really hate giving them the stuff, but I know we have to.  So maybe the worming has something to do with it?  But with the litters before it lasted quite a few days, and in the case of the previous litter, did not occur simultaneously with the day of the first worming.  And I don't recall this happening with the litters of other females.

This is the age I normally start introducing sloppy weaning food anyway, so Id' try that as long as they are well.