You have S11 < -10dB (VSWR better than 2:1) between 2.1GHz and 2.6GHz, so the antenna resonates on the desired 2.4GHz frequency.
Bow-tie antennas are wideband antennas, but placed in a 4x1 array configuration, the electrical length of the feed line segments would affect the overall S11 frequency response.
For example if the feed line segment is λ/4 at 2.4GHz, will not be the same at 2.2GHz.
Have to evaluate also a single antenna element (part of the array) and the coupling between antenna elements (which may need to be adjusted for desired directivity and minimum side lobes).