Yes, your birds look like red sex links, which is a description, not breed.
ISA Browns is from a patented line of birds, and the name "ISA Browns" is probably trademarked also. Famous name, top quality.
"Red sex links" is a descriptive name. Means the bird is half Rhode Island Red and carries the red color gene. The other parent can be any number of breeds carrying the silver color gene. Bred together, the female chicks are red, and the male chicks come out white.
So if I remember right, the mother is Rhode Island Red, and the father can be White Rock, Delaware, white Leghorn, Silver Lace Wyandotte or White Rhode Island. Because of genetics and where the color gene in this combination is carried linked to sex, it only happens if the hen is red, male silver, and not the other way around.
Typically, the chicks grow up into hens, mostly red with some white underfluff and some white tail feathers.
The big agribusiness companies have put big money into breeding their lines of Rhode Island Red into producing as many eggs as possible as soon as possible - beginning to lay at 18 to 20 weeks instead of 24 to 32 weeks like traditional breeds. And also have done extensive research and money for lines of silver-gened birds to cross them with to make red sex links. Each company gives their birds their trademarked name. ISA Browns are famous for being tops in quality. Other companies doing the same with their own line of birds gives them their own names like "Comets" (by Hubbard company, also famous for quality birds) "Indian River" "Syl-go-Links" "Cinnamon Queens" "Red Stars" 'Martis Rock Reds" (which may be black sex links).
Black Sex Links are also half Rhode Island Reds. the other half is Barred Rock and the chicks are sexable by color.
There are also now gold sex links, brown sex links. And all the new names make it very confusing to learn chicken breeds.
All the different crosses, all the different breeds that can be used for the silver gene, is why the temperaments and health vary so widely in red sex links, as previous poster noted. Another reason is the different lines of Rhode Island Red used vary widely in temperament and health.
European companies are now coming into the US market with their crosses and many new trademark names, like the Tetra Tints, and the Rouge birds from France called Freedom Rangers or Colored Rangers here. All are crosses that cannot duplicated by the consumer, insuring their market for their product.