If they were mine I'd have wormed them as soon as they started to be mucky.
If they've been scouring for a week they'll probably be dehydrated and needing electrolytes now. Vitamins would probably be useful, too.
If they've got fresh water to drink, the ewe should take that herself, but lambs won't always drink water; they just go to the milk bar. You can check if he's dehydrated by pinching the skin; if you can see a 'tent' briefly after you let go, he's dehydrated. If so, I'd get Pfizer Scour Formula or Rehydion or something and give the lamb 24 hours on that.
If their hydration is okay but the lamb is dull, then vitamins.
I'd worm them both, hydrate and give vitamins.