In order to resolve your issue, please troubleshoot with the following steps : 
The first thing you must do is to remove the faucet head, then turn on the water and see if the water pressure has improved without having the faucet head on.

If it has not improved, you must remove the check valves.  If you require assistance on how to do so you can reach a customer service representative by phone (number will be listed at the end of this message). If you remove the check valves and you are still experiencing water pressure issues, contact us for a replacement cartridge with you receipt in hand. 

You may reach Kitchen & Bath Customer Service at 1-855-629-3992. 

I hope this will help you. 

Thank you, 

-Conglom Kitchen& Bath Customer Service Team