Well, if they're 15 to 17 days old, you must be doing something right.

At this age, the Kaytee is the best thing for them. In a few days, say around 18 days old, you can start introducing them to seeds.
What I do is about that age (or earlier), I start giving them seeds one at a time. Just pop one in their mouth and let them swallow and get a taste for them. You can also put a small amount in a bowl and "peck" at it with you finger and get them interested in WHAT is in the bowl. It will take them a few days to get the hang of picking up and swallowing. It's all part of the learning process. You can also teach them to drink water the same way. Put some in a small dish and gently put their beak down in it. They will eventually learn to drink on their own. After doing these two things for a few days, they'll be eating on their own. Now, at this age, you sometimes have to "remind" them to eat and drink, by simply showing them the food and water and then they'll do the rest.
At 15 days old, you can still do the "seed pops", but don't expect them to eat on their own just yet.
In the wild or in a loft setting, the parents would be feeding the babies whatever they're eating themselves, whether it be seeds or french fries or bread. (don't feed them ff or bread though

)........I'm just saying that they would be getting "solid" food at this stage if the parents were feeding them, so popping some seeds in their mouth isn't going to hurt one thing.
I've had babies self feeding at 16 days old, but they were getting seeds from about 10 days old.......like I said, it takes a few days for them to get the hang of it.