Both my kids had their sounds forever and enjoyed books, but weren't necessarily early readers. My son has not been fully tested but some testing and achievement indicate he is at least HG. He jumped about 5 grade levels of reading in 9 months. He is reading high school level (although generally self selects books at the jr. high level) as a 3rd grader. Neither of the kids had interest in early reader type books, even while learning to read. My daughter just turned 5 this summer, so we're still trying to figure her out. We probably won't have her tested unless we see signs of an LD or need to for some other reason. She is tracking a very similar course to him so far. I consider both my kids to be kind of couch potatoes.
I would watch your 3rd daughter closely since you have 2 HG+ kids. 4 1/2 is quite young for testing and that score could easily be wrong. Especially if she moves beyond her rookie readers quickly. Watch and wait! They might surprise you. There are a lot of pieces that go into early reading including level of exposure, ability to track text, motivation, desire, etc. LOG is just one piece of the puzzle.
