Here's a discussion about Cellfood. I wouldn't waste my money, personally.
Meanwhile, some general thoughts on "supplements:"
1) If a health related product is efficacious it will be regulated by the FDA. If it's not regulated it's efficacy is negligible.
2) If a product IS efficacious (like a multivitamin) it will be based on a nominal 150 lb body weight mammalian metabolism. A chicken is, what, about 3 pounds? So you'll use 1/50th of a human dose, just based on body mass. Then you get into the differences between mammals and birds, metabolically. Medicines and such are tested with creatures as metabolically similar to humans as possible, like mice, rats, guinea pigs, monkeys, dogs or cats.
3) Your chickens may be adjusting to the changing daylight balance and timing as spring progresses. Feed them well, give them plenty of water, and make sure they have calcium supplements. Check for mites, stress sources (like neighborhood cats harassing them) or signs of illness.
My Red Star, who has never taken a day off, appears to have taken today off. I suspect springtime. She'll probably go nuts in another week or two.