I use the 20% flock raiser most often (oyster shell on the side for layers) since my flock is ever changing. But 24% is not too much IMO and I sometimes feed a 30% protein turkey starter (made by Purina but not stocked at TSC). I bred and hatched Silkies for a few years.. they were WAY too broody for me so I don't keep them any more.
Also note it isn't always just protein content that matters but the amino acids.
Really Dumor is not my favorite brand even though it is made by Purina for TSC. I can't believe the Purina chick starter is 18%.. by that I mean shocked... I swear back when I first kept chickens it was 22%. I think the nature wise is also made by them as the parent company. Their "meat bird" formula is 22%. Back then meat bird feed was 25% but changed in the past few years. I would try the 24% and see how your birds like it and do. Second suggestion would be the flock raiser... Either mix with your old feed as suggested or seal up your old feed and store in a cool dry location until the new bag is used up.
Poultry nutri drench is a great supplement and even has some amino acids. Giving vitamins counter acts the effect of the medicated part of the feed and should not be used if treating for coccidiosis. But if all is dry enough with lots of space and the water is poo free no one showing any symptoms of coccidiosis... it would be a nice boost. Feeds are often formulated to meet a minimum need... sometimes it isn't enough for an individual and a little extra in this case won't hurt those who may not particularly need it. They may benefit as well even. No supplement should be given more than 10 days in a row.
Try not to forget that sometimes it's just different genetics. I'm not 100% sure that splay leg isn't genetic, and that's why I cull for it.
Hope she thrives!