I had twins just the same two weeks ago - we call them the pea pods. Full term to a hogg. I spent every four hours in her pen getting them to feed for a couple of days then as soon as they saw me arrive they went straight under. I did milk off some colostrum from her 30 ml each and tubed them at the start to ensure were fully covered. I always have some to hand also in the freezer as build up a stock from older ewes as they lamb in ice trays just in case. Another thing I gave every new born lamb and these twins every couple of days is something called lamb thrive which you get from any ag supplier - they all have own brands but full of probiotics and vitamins which is said to help boost and prevent scours and watery mouth and so far this has worked for all ours.
Its hard work but will be worth the time in the end. Good Luck xx