Thanks for that Kaz, very interesting. so far chicks 1 and 2 look to be growing back normal feathers and doing well, chick 3 is growing back feathers but they are really ratty. I don't know if it will help but the diet that the parents were getting was their normal seed mix, soaked hulled oats, some pellet crumble (but I don't think they really ate much of that), and vegies which included Bokchoy, grated carrot, bean, radish and alfalfa sprouts, brussel sprouts, boccoli, sweet corn, parsely and basil. I didn't give any vitamin supplements during this time as I read somewhere that they can have too much which isn't good for the chicks.
I have 2 hens laying at the moment so if you can see anything wrong with the above diet please let me know so I can make changes if need be.
Thanks everyone for their support and help, I will keep you updated on the babies and the grow