Whenever they are sick, are they laying down, standing puffed up, or just puking? All three.
Puking up liquids of some sort (clear), puffed up, one of them is opening and closing their mouth like gasping, closed eyes, etc.
Heat source, yes
I do water and feed them. I don’t give them the medicine as I live with my grandparents. Normally my Grandma takes the medicine in for them.
I would also start treating them with Corid asap.So far, Penny has blood in her cage (she has crook back and a very nasty additude to any other chickens who get attention!) that’s on the chips.
Photos of where they are being kept would be helpful as well.
Corid dose 1 1/2 teaspoons Corid powder or 2 teaspoons of 9.6% Corid liquid per gallon of water. Give for 5-7 days as their only source of water to drink.
Give the Corid water to all the chicks it won't hurt them.
It would be better, imho, to get some chick starter as well. The Grower/Finisher you have is only 15%protein. Growing chicks need a higher protein. Get a chick starter that is 18-20% protein.
Make sure the chicks have a place to get warm, but don't overheat - they need to be able to get away from a heat source.
Puking also sounds like a crop problem. Make sure they have poultry grit (crushed granite). This can be found at Tractor Supply as well. Ask someone at the store to help you find it. Even if you don't give anything else besides poultry feed, some chicks will eat bedding which can impact the gizzard, they can't process that without grit.
Let us know how they are doing.