KaCee has dry, very flaky skin. She isn't itching, so it's not bothering her but it sure is bothering me

Is there a really good shampoo/conditioner out there that everyone uses? I just looked through some old threads and saw someone mention that food could cause it...she is eating Science Diet small bites right now but I'm thinking about switching her to Merricks if I can find it. Any suggestions would be greatly appreciated!