Note: this article is based purely off my own experience. Results may vary, however, I swear by these treatments.

I'm all for fixing any problems my chickens have with a cost-effective option. Surprisingly, most of my findings were accidental, but my results were astounding. These remedies have helped me and all my flock, as I hope they will help you and yours.

This one herb has helped me more times than I can count. It has properties to fight off infections and diseases, but what I've found is that garlic can be used for more than just medical issues.
Chicken bullying- I've used garlic on countless occasions when one of my chickens is being aggressive, and all other methods to discourage this behavior just will not work. I use dried, powdered or granulated garlic, though fresh garlic should work as well. Add about 1 tsp. to a plate of some treats for them and they will have a healthy treat.

Appetite Stimulant- Although I can't explain why, if I feed garlic (the same method as mentioned above) to a chicken that is not appearing to eat much, his/her appetite soon improves. (Also to encourage eating- put some warm water in a container of food and let the food absorb the water. They find it easier to eat this way and a bit more entertaining too.)

The "Active" Rooster

By active, I mean a rooster that wants to mate practically non-stop. It is normal for hormonal changes to cause this, especially if the rooster is around 1-2 years old. However, it can be stressful on the hens and the rooster may even prevent them from drinking and eating.

For this I recommend isolation, where he can see the hens but not touch them. Another method that worked great for my rooster was holding him while he was still on the ground, but limiting where he could go for only about a minute. I found that he wanted to escape, especially when a hen came near. He got mad at me, but after a little bit, realized that as long as he struggled, I would not let him harass my hens. He soon calmed down, and once I let him go, seemed to be more cautious. I had to repeat this whenever I noticed he was being too aggressive towards my hens, but after a couple weeks, he calmed down. No harm was done to him in this process, and it has had lasting effects for me.

Egg Eating

Until recently, I never had this problem. My hens started eating eggs only for the yummy egg inside, and left the shell with only a small hole in it. I had not changed their food or environment, but one hen laid a soft shelled egg and they discovered its deliciousness. Since life prevents me from being at home 24/7 to collect eggs, I had to find another way to break them of this. I walked in one day on my culprit- a hen eating 2 eggs in a nesting box, and enjoying the egg. Once she was done, I took one of the mostly-intact eggshells inside, filled it with mayonnaise and mustard, and gave it back to her. She was eager to eat it, but after a few bites, found out that it was not what she expected.
Note: If your flock lays more than one color of egg, I suggest performing this with all the colors. The chicken may think that only a certain color of egg has that nasty taste, and instead eat all the different-colored eggs.
If you suspect they may be eating the eggs because they need more calcium, simply provide your flock with a side dish of oyster shell or another calcium supplement.

Moist Food

I've had a couple occasions where a chicken was bullied and became apparently too depressed to eat, so her weight began to drop. Running out of ideas and since she refused to eat the dry food much (even from my hand), I finally tried some moist and warm food to feed just to her. On every occasion that I've done this, my chicken fell in love with this "new" food and was happy to eat it. I would isolate her for a few days, providing her twice daily with this moist miracle and also leaving some dry layer food and fresh water with her. Using this method, my hens were able to perk right back up within a couple of days, and their weight became normal within about 2 weeks. Placing the dry food with them helped to show them that they should eat that as well, so that they don't become too reliant on me feeding them special food forever.
The advantage to feeding moist feed at times like that and others, such as when a chicken is sick, is that it is easier for them to process and they are able to take in more of the nutrients from the food. Since it is moist and softer, their gizzard doesn't have to work as hard, and the chicken can concentrate on healing.

Chicken Wounds

Sadly, it's something we all have come across and will continue to come across for as long as we own chickens. It's never a pleasant experience to go into the coop, only to find a chicken hurt and bloody. However, this has been easily treatable for me and my flock.
I highly recommend a spray called Blu-Kote, which can be found at most farm stores. This spray has 2 major benefits: it kills bacteria in the wound, an covers up the color of blood. However, if you do not have Blu-Kote and can't find any, I have used antibiotic creams (like Neosporin, WITHOUT any pain meds ending in -caine) and just a simple rinsing of the cut, with a bandage applied afterwards. These treatments have worked during times that I thought I might even lose the chicken.
If your chicken has been attacked by a predator, vet help may be required. Animals have bacteria on their teeth that can cause a very bad infection in a chicken, so the vet may have to prescribe antibiotics to help heal your chicken.