When the tip splits down the middle, this is due to:

Using a tip that is narrower than the nail plate can cause the tip to split down the middle. When the tip does not adequately match the width of the natural nail, stress is applied unevenly as the nail experiences pressure during daily activities. This misalignment can result in a weakened bond and the tip failing, typically manifesting as a split. Ensuring that the tip is correctly sized to fit the natural nail allows for better adhesion and distribution of stress, thus preventing such issues.

In contrast, excessive filing can lead to damage or thinning of the nail, which affects its overall integrity, but it does not directly cause splitting down the middle. Inadequate curing relates to issues with gel or acrylic products not setting properly, which can cause peeling or lifting but not specifically a split in the tip. Improper application technique may generally lead to various problems with nail enhancements, but without the specific issue of width mismatch, it would not directly cause the tip to split down the middle.