Know it sounds harsh but trust me it works-dunk their face gently into the food and some will look at you like your trying to kill them but some will think Mmm it's quite good this and once 1 starts to eat the others will follow,or roll them in and remove mum so they have to clean each other or/and themselves
Also rice pudding with a touch of honey, egg yolk and honey, pilchards mashed to a pulp,let us know on their progress and of course mums