I'm not on MRC but I do fly a lot so I figured I could answer from that standpoint
I would definitely check any liquids, there should be no problem as long as they are labeled, in their original packaging, and in your checked luggage. It is not necessary that they be in their o.p. but it might help to avoid having your luggage searched manually. If you are worried about the powders, I would check those as well. However, I flew two months ago with a 1 pound tub of protein powder in my carry on bag, and there was so problem at all. However, the original seal was still on the container. As far as I know, there aren't any rules about flying with powders, but to avoid having things confiscated, I would check anything that you're iffy about.
Have a safe and wonderful trip!