Is the little one drinking? If not, grab it up with index fingertip behind head and gently dip its beak into the water. They should have it figured out in a couple days. Try yogurt or kefir with LIVE cultures to get their gut flora going for all of them, not just your slow starter. Your medicated starter will likely kill the good bugs too....

Have never fed medicated starter. Hatchery chicks are always shot up for Merek's so you're good. Get a bag of Scratch & Peck or Modesto Mills starter. Call around to source or go to their websites to find distributors. Are you prone to trusting 17 yo girls?

Give the slow starter some more time to see if it can pull in together with good support. They sleep alot the first few days and can run off their yolk bank account during that time....