In the books the current state of the other two dragons is far better IMO.
There was a plot line in the books that resulted in a different outcome for them at the end of book 5. That plot line was not present in the TV series unfortunately.
By the end of book 5, one could say that all three dragons had risen greatly in their dragonhood, with Drogon being at the top of the heap of course, since he had spent considerable time flying around free, while the other two remained confined, which inhibits the growth of dragons.
Nonetheless, Viserion and Rhaegal did what dragons are supposed to do.
I wish we had been able to see that in the series.
The special effects guys are saying that all three dragons will be much bigger next season.
And Quentyn’s famous quote - “Oh...”
hahahaha