I've found that my birds don't particularly eat their normal food very well during molt.
To peak interest, I make them a wet mash of feed, water and buttermilk. I also add B-Complex to the mash. Not sure if the buttermilk gives a little tang or what, but they gobble it down. I usually make the mash the night before I feed it, but if you let it soak for an hour or so that should be sufficient.
I feed a 20% protein feed year round, so don't necessarily offer extra protein, but if you are using layer feed that's around 16%, I would consider offering a little egg, fish or meat for a protein boost or if you have chick starter or all flock feed (18-20% protein) that would be good too.