Twin lamb disease is a bit more serious than just a lack of energy, although it caused by a lack of sufficuent energy in the diet, usually because the sheep are carrying too many lambs and don't have the body capacity to eat enough food to meet their energy requirements. In this situation they start to break down muscle to meet energy requirements causing ketosis - BAD.
Treatment is very difficult and if you are getting lots of success with twin lamb drenches then your sheep probably haven't got true twin lamb disease. Mortality tends to be about 90% once ketosis sets in.
If you can get them eating then they might pull through, egg yolk, milk and black treacle is as good as any lamb drench you can buy - provides energy and something to get the rumen working. If the ewe lambs or slips her lambs then she has a better chance of survival.
It is a depressing thing to treat as treatment is generally so unsuccessful - but can be prevented to a large extent by good management