These are the only treats I've tried so far. I love giving them treats, I'm just wondering how often is it okay for them to have stuff like this?
IMO they can have all the above. Just limit the daily intake to no more than 10% of their diet and provide grit for them.
Another tip...I find that my chickens have always loved "wet food". I put chick starter (in my case their regular poultry crumbles) in a bowl, add warm water, chop up some of their goodies finely, mix it in and put it on paper plates or a bowl that you will feed them out of. If you have several chicks, 2 plates work well. **Warning...they will scratch and sling wet food and make a mess
Mine are older and laying, but they love to get "wet mash" everyday, if I make it. I use an all flock type crumble and then mix in things I have on hand, like kale, apple, sunflower seeds, oatmeal, veggies, etc. Occasionally I do mix a little vitamins in the water that I make the mash with. I do use the higher protein food, so I give them extra veggies, weeds, fruit, etc. on days that I don't do the "mash".
I do leave their dry feed available at all times in the coop, so they think the "mash" is a total treat, but it incorporates their poultry food with goodies.
Just my opinion