Isaac, is there a rooster with those hens so the eggs are fertile? Unless there is a rooster the eggs will not hatch. I think what you mean is that the Brahma hens do not go broody and incubate the eggs themselves but I’ll ask a silly question.
Is it possible to let the local hen that hatches the eggs raise the chicks for about 3 to 4 weeks? In Ghana you have a warm tropical climate, it just doesn’t get that cold. If that hen can raise the chicks for 3 to 4 weeks you do not need not provide any heat for them. That is the easy solution if possible.
Too much heat is as dangerous to chicks as too little heat. In your climate you do not need much heat, a fairly small wattage bulb should work well. Your goal is to have one part of the brooder to be around 32 degrees C but have other parts cooler if you can. That way the chicks can move to comfortable parts of the brooder as they wish. It’s not a matter of how many watts, it’s a matter of keeping one area warm enough. In your climate it will not take much.
One summer here I had daytime temperatures above 32 C during the day and not much lower than 32 C at night. I turned the daytime heat off at 2 days and the nighttime heat off at 5 days. They did fine, they really did not need the extra heat. In cooler temperatures I provide more heat longer.
I personally do not use any medication or add anything to the water or food. If you are taking care of the chicks instead of the hen that hatches them, the most important things to do is see that they have clean water and keep the area you have them in dry. If you can do that they will probably be healthy.
Chickens do not have teeth so they cannot chew their food. They eat a lot of things that they need to chew. They have an organ called the gizzard that chews food up, but that needs small pebbles to act as teeth. If you give the chicks access to the ground you will see them pecking at the ground a lot. One of the thing they are doing is eating small pebbles so their gizzard can chew food up for them. If you do not give the chicks access to the ground, take some dirt with small pebbles and let them pick through that. We call those small pebbles grit, but the British call it insoluble grit. After they get grit they can eat about anything you eat, vegetables, grains, or about anything else. But it needs to be in small pieces for them.
Good luck. Chicks aren’t that hard as long as you provide enough but not too much heat, clean water, and keep them dry.
