Thank you and for your answers. I figured out the issue and it was because I used the BIG-IP's IP as the default gateway for my web servers. I am studying for the 101 & 102 so my lab setup was a step by step process based on the video tutorial I am following. It was when I got to the part that talked about floating IP, then I realized I could use a floating IP as the default gateway of my web servers and that worked for me.
Your suggestions are also great to be used for other scenarios if I encounter them. Thank you both, I will appreciate your help.