Those are young ones PRL growing beautifully. They are enjoy shirakura ebidama shrimp food.
Crystal red shrimps are pretty picky when eating. I have several different food on hands, and switching between. My shrimps favorite is shirakura ebidama/ebidama specia. This is their main food. And I also feed them hikari shrimp cuisine, and a new food I recently introduced in, glasgarten shrimp dinner. Sometimes, fish food hikari algae wafer is acceptable, too. :)
Another benefit from a variety food sources is a more balance diet. Different brands have different formula. A more balance diet will keep your shrimp healthier and happier.