I've been sent many formula samples through the mail that are already pre mixed 2 ounce little bottles. The problem is they're all different kinds. A couple are simalac but they're mostly enfamil, just different types (ex: newborn, infant,gentle) it's very kind that I got sent them and I'm extremely grateful because there's a lot, but can I even use them all? It scares me that they're all different and I don't want it to upset my baby's stomach. However, I would hate to just throw them away. Why would they send so many that are all different though? What would you guys do?