Dogs r active but eat very little their ribs r starting to show. They have been checked for any worms they also had a fecal test done and they r good... So now I go to there food. I was feeding them puppy chow, iams and now science diet witch they like, But eat very little... Is there any weight gainer or something to give them to have a better appetite... Help me out pleace! I have other boxers and never had this problem...

First can I suggest a diet change?
Those aren't very good brands and there are others out there that have a lot better nutritional value.
Being in Australia I don't know American brands but I have heard that Blue Buffalo is supposed to be very good.

Also you can try mixing something through the food to make it more appealing to them. My pup was a terrible eater when he was about 4 months. I mixed a little canned food or some tinned sardines through his food and he loved it.

shazamataz suggested Blue Buffalo, but I'm from the US and my vet highly recommends Iams.

I'm going to give you the same advice I gave Ston67:

Mix about 1/2 can of good quality canned dog food (I use Iams) into about 1 1/2 cups of dry dog food and feed them twice a day.

Once they start eating it all, you can increase the amounts of canned and dry food until they're up to the max for their weight.