I would definitely increase the %, and with that many fry you will NEED a tank of over 20 gallons to grow them.. that is another big reason they aren't growing - a grow out tank should be no less than 20 gallons (for a small spawn), 30g+ is more ideal for what you have.. 7 gallon is smaller than what a lot of people breed in.
So definitely do at least 50% daily water changes.. they produce a growth stunting hormone, and in such a small space it's going to build up quickly.
So.. bigger tank, make sure the temp is 80-84*F, feed 3-4x a day of BBS and for white worms.. this page may help
. There are other types of live food.. would look up what you can get and what you are willing to do (some live food is just yucky dealing with lol). But you definitely need to get them some more variety with the live foods.. BBS is easy and is good to feed, I'd go that route mainly at this point.. anything else is a bonus.
As for food other than live foods.. I have New Life Spectrum fry formula
, along with some fry food I got from the IBC store (no real name to it). Once they get a bit bigger then you can move onto small pellets, NLS have a "growth" formula that I love to feed my young ones.
But at this point, I would stick with as much live food as you can..