That's kind of strange that you lose mass when you cut. If you are following lean gains, you should be pretty high on protein. Combine this with resistance training, and you should be conserving lean body mass on a deficit. How do you know you are losing muscle? lifting numbers going down or staying the same?
I find it hard to lose fat and gain muscle at the same time. I usually shoot for one or the other. If you want to put on some mass, you might want to add in some squatting/dead lifting to your workout. I would adjust your LG on/off day percentages to either bulk or cut. The standard body recomp -20/+20 is kind of a hybrid bulk/cut and I think better results come from a more specific goal.
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