Chihuahuas are known for eating anything they can get in their mouths. So they tend to get stopped up from time to time.
That could be said of many different breeds. For example Labs will eat anything that doesn't try to eat them. Currently my 1/2 Great Pyrenees/1/4 Lab/ 1/4??? has a feddish for phone books. She consumes the covers, and shreds the rest of the phone book. Needless to say I have to more often than not use Internet searches to look up phone numbers. Foil candy wrappers if left around is another favorite for both my dogs. My prior dog enjoyed crunching into hicory nuts. I'm sure others on this forum could come up with a more wild range of items.

As for my vet being flippant can you explain why you would say that?
The response of: She said that they like to eat a lot of different stuff, and so of course with a small system it gets stuck sometimes is a non-answer. Did she ask you about the diet? Did she ask about water consumption or how long the periods between urination? Did she ask how much exercise the dogs get? Did she run any blood tests? Did she address the problem and provide a possible solution?

As a side thought you might consider adding green beans to the diet. Start out in small amounts. It can readily cause diarrhea if the dog eats too much of the green beans. Increase the physical exercise of the little ones. Perfect excuse for supervised play with the GP puppy. It's extremely doubtful the Chi is being scared into constipation by a playful GP puppy.