We used to have oxytetracycline tablets from the vet to give to multiples or any lambs slow to suck, the tablets were only about 10p each and the vet would dispense small numbers so you could maybe ask about these if you want to have something to give just incase, worth having for a few pence. When we started with sheep and lambing we were told that we would need to give a tablet to every newborn lamb.
We now keep spectam in instead, however having said that we only occasionally use it on newborns, we have found that if you make sure that the lambs have colostrum soon after birth then they are fine, we generally tube feed colostrum (needs to be freshly milked or stored frozen rather than the formula) if lambs are being slow to suckle initially, so at least we know that they have definitely had a good drink. We do use it if occasionally a young lamb develops any scour later on.
We lamb over 6 weeks or so and the pens will be reused, we don't muck out except to remove anything on the surface such as afterbirth as I think full muck out of the pens would cause more contamination spread in the barns with potential for debris to be dropped. We do sprinkle hydrated lime liberally in the pens and add plenty of fresh straw. Have probably only used spectam on a handful of lambs out of 100 born this year, the lambs have remained in the mothering pens for 2 to 3 days generally and then gone into small groups inside.