Nice light shirts. These are the smallest 2 shirts my daughter has. Not exactly 18 months, but close. Depending on how complex your child is (mine is skinny) you can increase the size.
Adorable TABNIX Toddler Little Girlsβ Short Sleeve T-Shirts: 4-Pack Graphic Cotton Tops for Size 2-7 Years
44 Review
Stylish Woxlica E Girl Clothing: Trendsetting Graphic Print Summer Crop Top for Teen Girls
43 Review
Amazon Brand Sleeveless Chambray Multi Dots Girls' Clothing
62 Review
Spotted Zebra Girls' Short-Sleeve Flutter T-Shirts: Amazon Brand for Fashionable Kids
43 Review