Your Berkshire x GOS need a pound of food per month of age, up to a maximum of 5 lbs per day - if you're feeding lots of fruit & veg you can reduce the hard feeding a bit, but no more than 50% or the growth will slow and they'll struggle to maintain themselves, let alone grow when the weather gets colder. 4lbs of fruit & veg = 1lbs of pig nuts.
Our Kunekunes get 1-1.5lbs per day each (split into 2 feeds) and usually topped up with fruit & veg or hay/hayledge when there's no grass. They're slower growing, so aren't likely to be 'ready' til they're at least 10 months old whereas your bigger ones will be ready sooner (around 6 months)
No barley or grain for your Kunekunes or they'll pile on the fat
As long as they've got access to grass/hay they'll be fine. If it gets really cold we soak sugar beet pellets for them, but feed sparingly to avoid them getting fat - half a pound per day is ample for each pig.
I'd probably suggest separating them at feed time and if possible give them separate areas to live in too - the crosses will root up the grass that the Kunekune need to eat.
Hope that helps and makes sense ?
Karen