First, and foremost, fry are SOOOOO little that it is difficult to see them eating anything - with the exception of "marker" food such as orange/pink brine shrimp. I have terrible eyes, yes, but I think it is tough for most to see those tiny tiny things and determine whether or not their tummies are full.
I have recently come into GREAT respect for those who have successfully raised just a few fry. I have always had 100s if not 1000s to deal with. This latest hatch is 2. That is right. 2. It is IMPOSSIBLE to make sure that they are eating regularly. It is very difficult to even FIND them to make sure they still exist. Raising just a few is a whole lot harder than raising thousands.
That said, they DO seem to be eating the gel food I put in. I started by hatching baby brine shrimp, but when I pulled out the breeding grass and only found 2 fry, I stopped. It was not worth it. I then tried dropping in small pieces of frozen bbshrimp. I suppose they were eating them, but I could not tell or see, and I was getting messy water very quickly. I decided there had to be a better way.
I resorted to the gel food for these two fry. It is successful - and both have tripled in size (that is not saying much - they are still tiny tiny tiny - but one is big enough to find rather quickly in the water, now!).
I mix up 2tsp freshly hatched baby brine shrimp with 2 T ground fish flakes, a bit of spiriliana flake sifted "dust", 4T water and 1 package of gel. This is cut in 1/4 inch cubes. A single cube will feed 25-50 fry for a day when they are under 2 weeks of age. If you only have a few fry, you may never even see what they eat. Look at those little things. They are barely more than a line and a dot - their tummies are smaller still. They need a steady supply of food through the day - but not much. Take the cube out at the end of the day if it is left.
I bet yours are eating. They are not dying, right?