Life prolonging procedure vs life support, there is a difference between ordinary and extraordinary procedures, notice you don't care to post that, just any definition to support you.
Florida law does not differentiate. Perhaps you don't understand,
"any medical procedure .... which sustains, restores, or supplants a spontaneous vital function."
That definition qualifies Teri Schiavo who required a feeding tube to remain alive after losing the "spontaneous vital function" of swallowing.
And I picked chaivo for a reason I figured that you would agree, so why not agree with removing feeding from a child, elderly w severe dementia, pretty much anyone not in charge of their decision. Notice I made the distinction of ordinary and extraordinary. The bigger question is why does it become wrong to have a late term abortion? It's still on "life support" received from the mother. That's the main question
You didn't ask about removing feeding entirely from a baby. You asked about two specific foods; breast milk and formula. If you want to change your question now from that to not feeding a baby at all, the answer is no, unless one want to face child neglect charges, they cannot starve their baby.
The difference in the Schiavo case from a baby is that Teri, while still cognizant, purportedly conveyed to her husband that she would not want her life sustained in such a fasion. A baby, incapable of rendering such a decision, is forced by the government to be kept alive in cases where the parent(s), or other guardian(s), refuse to.