I have 4 chicks 2 are 5 weeks old and 2 are 6. I'm concerned because they have prominent breast bones I feel everytime I pick them up. They have always had free choice feed and fresh water. I add ACV and probiotics and occasionally electrolytes. They are eating and drinking. They have sneezed a little but have otherwise acted normal I believe? Should I worry or will they just fill out as they get older?