not excatly sure but if i were you i would completely change my juice recipe. the body need different nutrients from different foods. its possible your body is telling you that the same food or juice everyday isn't cuttin it. also beets are very intense, i only do beets for a couple days then leave them alone for a couple weeks. same with beet greens - very intense, may be too much for your body everyday.
get yourself one of those cheap juicing recipe books on amazon like one by steve meyerowitz or jack lalanne and vary your juices up every day, or every other day.
try some cabbage/apple/ginger or maybe carrot/apple/lemon or pineapple/cucumber or ???
fruit juice in the morning is a bit easier on th tummy also. fruit juice with some lemon and ginger added is a tremendous breakfast juice.