So sorry to hear of your losses...this is just our third year with the meaties (Cornish X) but have raised them successfully so far, my dd's annual 4-H fair projects. We do not withhold the feed at all, the first bag is medicated turkey starter (Purina) and then we switch over to Purina Show feed for the rest. We only raise 15 at a time, 3 of which go to the fair, the rest in our freezer so by no means are we experts like some of the folks here, but that has sure worked well for us.
The weather has been a challenge, heatlamp on the first 2-3 weeks, then on and off day and night when it got in the 40-60's...then fans on when it got in the 80-90's after they feathered. We are at the 7 week mark and so far so good, but it is a constant adjustment with them I think. And they go through a LOT of water--fresh water refill twice a day.
Best of luck--don't give up or get discouraged, it really is a learning curve but very do-able!
PS: If yours are only a week old make sure they have a draft-free brooder and a heatlamp where they can stay underneath if they need warmth or move away if they are warm enough--at a week they still have their fluff and cannot regulate their temps too well. Not sure where you live but rule of thumb is 85-90 degrees the first week (do you have a thermometer in the brooder?) then decrease by 5 degrees every week until they are fully feathered...