Zirna looks healthy and happy. Depending on the age, rats also slow down with age. I have male rats , so I can't say for sure with females, but my baby males were balls of energy and have just started slowing down. Not to the stage of an old rat, since they still chase each other and play, but they aren't as energetic as when I got them. As lilspaze mentioned, she may have sprained her foot and is just taking it easy. One of my babies ended up doing this and he was fine after about a week and was back to zooming through the cage and picking on his brothers.
As for Iris, I'd recommend setting up multiple food and water stations. Rats can be possessive of food and water and having multiple bowls of food, water, and multiple water bottles, minimizes any aggression or possessiveness. If I see a rat is picking on others or pushing them away from one of the food bowls, I'll move them to another feeding station. I have three food bowl stations, two water bottle stations, and a big pool with rocks.