Carnitine brands

Recently I switched l-carnitine brands for insurance purposes. I started feeling extremely tired, including legs not working well and digestive system slowing way down (both have been pretty good recently). Normally when I am tired there is a very long list of possibilities of what could have caused it, but this time it was fairly obvious it was the switch in brands of levocarnitine. When I switched back, I returned to how I normally feel. The brand I feel good on is l-Carnitine Pure Encapsulations. The other I am not sure because of how the pharmacy packaged them. They were idividually packaged because they disovled very easily, were white, and were round and flat. I am not prone to allergies, so I'm wondering what went on. Have others had experience with different brands of l-carnitine?