
I'd start them now, but then I have started pups in my own breed as soon as their eyes open if I thought their weight gain was levelling off.
Are they showing any sign of int erst in Mums food (assuming it is offered in the whelping box)?
I start mine regardless at 18 days as I like to have them on solids before worming, finding it less likely to have problems with the worming if they have it after some food.