Here is the advise I give as an RD on juice and solids:
If you are using juice to meet all thirst needs then water it. If you are
using as a food (like for a kid who doesn't like many friuts and vegetables)
then don't.  Don't bother with apple juice, it's mostly sugar water. Get high
vitamin C juices like orange or other citrus or mango or apricot which have
vitamin A also.
A general guildeine is to have wheat be one of the last grains introduced
because it is such a comon allergen. That is where the one year guideline
comes from (as far as I know).
As for the iron with a 7 week premature baby I feel the blood tests are a
good idea to assess the babies iron status.  Or could the parents wait a
month or two and then try the supplements again?

RE: Yeast If the nystatian does not work after about a month gincien
(spelling?) violet will.  It will stain EVERYTHING it comes in contact with
but is a good last resort.