The rule for chicks is 95°F for the first week and then decrease the temp by 5 degrees every week until they are weaned from the heat. But not all the brooder has to be the same temp, place the lamp on one side so the chicks have space to escape from heat when they need it. To be sure the temp is right for the chicks you have to watch their behaviour: if they alway are all together and stay always under the lamp and never leave the heat, it's too cold; if they are always on the colder part of the brooder trying to escape the heat, it's too hot. Also, when chicks are unhappy they are loud and scream. If you meant the signs they are sick, then you have to pay attention if they are lethargic, not eating and drinking after 3 day old, poops of strange colors, also check them daily for pasty butt.
Don't mix medicated and non medicated feed, give only medicated feed or it won't have the same effect and maybe be uneffective.