I'd send the oldest, unbroke one for at least a month (just for further training) and just work your other girl. Play with her, ride her, become more aware of her little kinks that need to be smoothed out.
I say kudo's for not breaking Rain at two, four and five are perfectly acceptable and very healthy ages for training.
I just sent my just-turned-five year old to the trainer today. I'll be picking up my just-turned-two year old on the weekend from his breeders place. The two year old is still completely an utterly a baby, I couldn't imagine putting him to the trainers even at 2 1/2 or even 3. He's mentally not ready for it. He stands 14.2 and is built like a tank, but needs time to be a horse and learn horse-manners.
The five year old, on the other hand, is very mature and intelligent. He doesn't have his head in the clouds, is respectful, calm, and quiet. The trainer was very pleased with how behaved arriving, I expect he'll be a piece of cake to train.
Wait! I'll fix it....