Interesting again. My Tropheus Ndole babies (same Genus but not species) are not strict herbivores in captivity (I am not sure I believe there are any cichlids that strictly stick to a herbivour diet all their lives seem to remember seeing a clip of Tropheus joining in with eating fry of other species in the wild during times when this is easy). I have seen quite young (under a month old) Tropheus sp."red" take newly released Ophthalmotilapia ventralis fry I had in the same tank though the adult Tropheus left them alone. Maybe they had victim way of swimming or something?
Sorry not seen any cross fostering with my Tropheus or any of my mouthbrooders, except Tropheus picking up the eggs of different types of Tropheus or crossing in the past (I do not keep different types of Tropheus together any more). But then my goby cichlids do not breed much and what I get seems to disappear in a Tropheus tank I assumed eaten by either Tropheus or the other gobys.