Grinds are convenient but you need to incorporate bone in meat at least 2 days/week to ensure their teeth get cleaned and maintain jaw muscles. The grinds also need to have bone in it and if it does not you'll need to add bone meal.
You need at least 3 different meat sources from different animals. Feeding them only 1 source creates a high risk of developing a food allergy (as well as low quality of life). Try duck and chicken too.
Does the mince have organ meat in it as well? They'll need to get hearts for taurine and liver too. Too much liver is bad through so only give it to them in small amounts a couple of times a week with hearts. One day a week you need to give them a good organ meal other than liver. This would be like the lungs, pancreas, kidneys, ect. as they contain vitamins the liver does not have.
What I do with any is to add some water in their bowl to just barely cover the meat, not too much to where they have to snorkel for it but I'd say about half way up. This will keep the meat moist so it can sit in their bowl. They will stow the left overs but don't worry they'll go back to them when they're hungry. If you use grinds just mix some water with the grinds to where it has a near soup consistency (but not too watery) and that'll help keep it from getting hard and nasty by the end of the day, just make sure to add some bone meal (about 1/2 tsp per 4oz) to help prevent diarreah.
Depending on the size of the cage/enclosure you have, you can also consider feeding them a whole carcass. Just cut it open (rabbit, squirrel, ect) and let them go at it throughout the day.
Don't worry about them starving. If they will eat the turkey mince they will eat the other meat. Naturally, they will favor their favorite over new ones, but eventually they will eat the new meat, especially since they are still babies.
You may not want to mix kibble with their raw diet as it requires different digestive enzymes to break it down and will upset their stomachs.
Just give them their raw meat foods. I put my ferret's food in his cage in the morning before I go to work and again at night when I get home from work. Because your ferrets are young put in plenty of food for them to eat. They will eat when they are hungry. What I do sometimes is put half his food in which is thawed and then put in the other half still frozen. Throughout the day the food will thaw and he will have fresh food during the day when I'm not home. Then when I get home I give him his dinner meal.
Charlie Sept. 13/17-Feb. 16/23 DIP my little buddy