Nov will be fine , you say they are jan born so they will be 10mts old so stronger then most who will be 7-8mths at tupping , don't know how big they are but would it not make management easier if you put them all with the ram instead of having to separate with the chance that the ram or the lambs might jump the fence to get together , from your description they are all maybe 45kg+ so would be fine ?? For pregnant ewe lambs you have to keep them growing as well as keep the foetus growing so condition score regularly try to not let them loose or put on condition during the first 2 mths grass and good hay should do this ,maybe crystalix if both in short supply , maybe at the turn of the year start on sort of 300gms day nuts/pencils/ mix if you want to keep on with crystalix then reduce by 100gms , keep condition scoring ( just lay a hand on them while they are eating ) . if you don't scan then assume they are all carrying twins so in the last six weeks before lambing increase nuts to 500gms day split into 2 feeds . Always trying to keep them fit but not fat ,