Cut back your photoperiod, take out the caulerpa, borrow or buy a UV sterilizer, run a phosphate sponge in a canister filter, and some carbon and floss. Skim hard. And call Jayson at SWC for some clams.
You likely have had phosphates building up, and now they've caused this. I had green water like yours in a 90g for almost two months, but it cleared up when I took the steps listed above.
Chin up; you'll see your LR again!
(PS- watch your fish for signs of stress. My tang suffered, clownfish did not.)