I did consult a vet and they told me to use roudy bush instead of kaytee, so I’m feeding both because they told me to slowly introduce the other formula
Ah ok, I see. Yes, always good to slowly transition from one to another, just like any food.
they also gave me some vitamins because they saw that the chick was mildly dehydrated
That´s good. Natural unsweetened coconut water is also good for hydration if you notice the chick getting red.
I was meaning to write before, that it´s important you have a source of humidity in the brooder, not just heat. Because if you only supply heat, you leave the air dry and it can lead to dehydration. Humidity between 60-65ish range is nice. If you don´t know what it currently is, you will need a hygrometer to measure.
It´s great you are in contact with your vet, keep them up to date and in regular contact. Things can go bad very quickly with such chicks.
Did you show them a photo of your brooder set up?
I don´t understand about the peg, but ok. If you are worried about spraddle leg/splayed legs, be sure you´re doing all you can to minimise the risks, by having adequate bedding, aoid placing the bird on smooth surfaces - you can use a teatowel if you usually place them on a worktop to feed them so their feet can grip, be sure to tuck the legs under as you place him down.
Check that you are preparing the formula correctly every single time, using the correct powder to water ratio, and at 105F.