loonyx

Ok I have verizon fios with the package 15/2, i get the speeds I pay for but I am having a problem when downloading from FTP's. When I download something from a HTTP I will get the full speed of 1.5mb/s but when I download off an ftp it will max out at 600kb/s and will not exceed. But if I open up three ftp clients, and download at the same time, I will get a steady 500kb/s meaning I am getting the speed I want, but why cant I just use one client and get 1.5mb/s. I know it is not the server im getting my information from and I am pretty sure it is not my client. It just doesn't make sense. Can anyone help or provide an explanation?