(CNN) Americans Regan Smith and Caeleb Dressel claimed two of the five individual swimming world records that were set this week at the world championships in Gwangju, South Korea.
Two of those records belonged to their countryman Michael Phelps, the most-decorated Olympian of all time.
The first of Phelps' records was broken by Hungarian swimmer Kristof Milak, 19, in the 200-meter butterfly with a time of 1:50.73, beating Phelps' 1:51.51 from Rome in 2009.
"As frustrated as I am to see that record go down, I couldn't be happier to see how he did it," Phelps told the New York Times of Milak's performance. "That kid's last 100 was incredible. He put together a great 200 fly from start to finish.
"It happened because there was a kid who wanted to do it, who dreamed of doing it, who figured out what it would take to do it, who worked on his technique until it was beautiful and who put in the really, really hard work that it takes to do it. My hat's off to him."
Dressel, 22, broke the second of Phelps' records with a time of 49.50 in the 100-meter butterfly, topping the 49.82 Phelps also swam in Rome in 2009.
The trend continued when Smith, 17, broke Missy Franklin's world record in the 200-meter backstroke with a time of 2:03.35. Franklin set the record by swimming 2:04.06 at the 2012 Summer Olympics in London.
Russia's Anton Chupkov set a world record of 2:06.12 in the 200-meter breaststroke, and Great Britain's Adam Peaty broke his own world record in the 100-meter breastroke with a mark of 56.88.
Phelps' lone individual world record left standing is the 400 meters in the individual medley.