I gave mine a small worm today for the first time too. and some grit.
The RIR's wouldn't have a thing to do with it, until one of the yellow ones got it - then the RIR's turn into meanies despite being smaller.
In the end the yellow one tricked them - left it laying down so the RIR's ignored it then she grabbed it and sneaked off into the corner while they were busy scratching in the grit!