Just give them an extra protein treat, separate from their feeder. For example, I give my girls fish scraps, or scrambled eggs cottage cheese, yogurt, mealworms, etc. Depends what I have. Some people give cooked meat scraps, etc. You can offer them an extra protein treat a day in addition to the feed in their feeder. Do that for about 2 weeks and see if you start getting eggs more frequently. If you want more details on percentages of feed, see the BYC thread about protein, linked above. Some people purchase gamebird feed or calf manna and mix it proportionally. Personally, I wouldn't bother with that. If you're experimenting to see if your girls just need a little extra protein right now, try giving them something you already have available.