Sorry to hear this, I lost three triplets in the same way - the previous day they had been up and suckling well and the next day were dead, during the very cold spell we had (they were all indoors too!). Only one of them I had started to feed but it was too little too late, I think the ewes just haven't got the amount of milk this year as previously I've never had problems with triplets. My last triplet is now on the bottle.