So here is the reason that Kronk has been more irritated with Mira lately:
She really gets around fast. So she's interacting with him that much more. I think I've figured out the problem with Kronk, though. Kronk has had knee surgery on both his back legs. As a result he has chronic pain due to arthritis. The two times that Kronk has growled at Mira, it was when he was sleeping and she awakened him by touching him near his back legs. So I think Kronk was protecting his knees. As my mom pointed out, if Mira was a puppy, she would understand Kronk's growl to mean "don't do that" and she would learn to be careful around Kronk's knees. But Mira doesn't understand what his growls mean, so I have to teach her. Anyway, in the few days since his last episode, Mira and I have spent some time every day on the floor next to Kronk, with me petting Kronk and telling him he is a good dog and Mira just hanging out nearby, occasionally petting Kronk too when he will allow it. If he decides he won't tolerate it, he goes away and I tell him he is a good dog for doing that too because I always want him to feel like he can get away and I want to let him know that the right response is to just go away, not to growl. The other thing I've been doing is when Mira is on the floor and Kronk is lying down near by, as soon as I see Mira heading his way, I call out to Kronk and tell him "Look out Kronk, here comes the baby." He will usually then get up and move away from her and I tell him good dog. That way, he is never surprised by her, which I think was part of the problem. Lastly, any time that I want to let Mira play on the floor and I'm not monitoring the situation 100% (like when I step into the bathroom or go over to do the dishes or something) I make Kronk leave the room entirely. That way, Mira's interactions with Kronk are never unsupervised. So anyway, I think the situation is manageable, I'll just have to keep on top of it. Kronk has always been 100% fine with slightly older kids, so I'm holding out hope that he and Mira will eventually learn how to play together.