How can we read the two spectra? There is no vertical amplitude scale, and the horizontal axis does not have good numerical and consistent values (such as 100, 200, 300 Hz) or useful small divisions. Looks like there may be 1/4 x shaft speed present that is not normal.
Axial vibration on a centrifugal fan is normally not dominant. Possible causes of high 1xSS vibration in axial direction are shaft/belt sheave misalignment, 2-plane rotor unbalance, thrust bearing damage, rotor or seal rub, loose bearing or fan base supports, or resonant structure/foundation.