Slightly more anemic than before

My son’s iron level was 10 at his 12 month check. His pediatrician prescribed enfamil multivitamin with iron. My son hated the taste. And I couldn’t give him for 2 months and after 2 months I found out a different brand on Amazon, We just started using it last month, sometimes forgot it skipped couple days. Today at 15 month appointment his iron was 9.7. His pediatrician ordered more testing. He thinks he could have thalassemia since I’m Mediterranean. I am freaking out here. Anyone experienced iron levels dropping slightly??? I have heard anemia gets worse over time if not treated. I hope that’s why and nothing else