Hi rosieyvonne
Never say never, but I think Mother hog will think her job is done now and will have left them to their own devices. She will, likely, either be hibernating already, or fattening up in preparation. Mother hogs have done an enormous amount of work in bringing up and feeding all those hoglets, so she may need a bit of time to herself to put on weight.
Re. the fish oil, I know it used to do the rounds that fish flavoured food wasn’t good for the hogs, but apparently it was a myth. This link gives lots of information about feeding http://www.valewildlife.org.uk/wp-content/uploads/2018/04/Feeding-wild-hedgehogs.pdf
There are so many brands, etc. of dog/cat food, that everyone would probably suggest something different! But as long as it is good quality it should be o.k.
You must have been doing a pretty good job to have 3 hoglets up to those weights. The important thing is to keep offering them food until they decide to hibernate (if indeed they do. Some hogs decide not to).
Some information from ‘News’ from Hedgehog Street’s Hedgehog Officer:
https://www.hedgehogstreet.org/should-i-keep-feeding-hedgehogs-over-winter/
It’s always worth checking out ‘News’ from time to time for interesting new information.
Good luck.
