I use TOTW for my 4 dogs and have for years. I am fully aware that it is not a favored food around here. Fromms is not readily available for me and has higher protein than I want. My 5 year old started on it at about 2.5 years and boy, did he pop width wise. The 2 year olds have eaten nothing but that since I got them as pups. I literally have never had to take them to the vet for any sicknesses - - they are a Frenchie and a Frenchie / Olde composite. My EB pup, who will be 6 months on Christmas, has never eaten anything but TOTW and the only problem he's shown so far is tear staining. I use Pacific Stream since the Frenchies shouldn't have the higher protein of most of the other flavors.
As to moving them now, if you expect the buyers of the pups to feed them whatever you have been using, you can do it but if they might choose another brand on their own it could be a lot for them to handle going through changing food twice in such a short time frame. Remember is should take a week or more to switch them out. One of the other breeders will have had experience with that.