I'd say if they're responding to half doses, keep it like that. 20-20-20 has a lot of big numbers, but that doesn't really mean much. It just means the content. It could be derived from anywhere. It's like the difference between an ounce of espresso and an ounce of earl gray tea. One's more potent. The guy at my local hydro store said for the most part, bigger numbers isn't always better. I'd stick with half doses, unless you feel more adventurous. This -is- your first indoor, you're going to experiment a little and find out what works for you.

At the end of the day, this is -your- grow set up, and -you- need to make the final decisions. Nobody on this forum, unless we can see every aspect of your grow op, can accurately tell you exactly how much of what you need to use.