when I first started with turtle breeding years back,I would feed them live daphinia and mosquito larvae,mysis shrimp etc anything that was moving was brilliant,daphnia especially had an action that seemed to attract their attention.As the breeding method was sorted and bigger numbers of babies needed feeding live food became harder to get in the quantities required so I just did away with it and used reptomin floating pellets which you could see little bite marks out of.Once a few start eating the others soon catch on and I also used to run the temp at 30 or so which got them going.To change them from live food to still can often be a problem especially if you have a shy one.Just persevere and have food in there if it wants it.I would not say it was a runt as such yet,but if it does not start to find an appetite it could well end up to be one.