Is Leg Weakness Due To HCTZ Drug Or Toprol Being Discontinued?

I have been taking hydrochlorothiazide for high blood pressure for about 3 weeks, and I am now having weakness in my legs. I'm unable to walk very far or for very long. In addition, I have just weaned myself off Toprol XL, a beta blocker. I've only been off Toprol XL for 4 days. Could the leg weakness be caused by the HCTZ drug, or is it a withdrawal effect from getting off Toprol?