Either the gain on the AMP is set wrong or your HU or other crossover setting is limiting the mids and highs to the speakers you want them to go to.
Check all/any crossover or bandpass settings first, then see if your front channels have a gain setting that can be turned up. (make sure you set the gain properly, it is not a volume knob).
If this doesn't help you might have a bad Amp or bad channels on your HU.
EDIT: Also agree that if you paid for install have them fix it first (or try).
Check all/any crossover or bandpass settings first, then see if your front channels have a gain setting that can be turned up. (make sure you set the gain properly, it is not a volume knob).
If this doesn't help you might have a bad Amp or bad channels on your HU.
EDIT: Also agree that if you paid for install have them fix it first (or try).