Depends, if C19:C26 contains addresses which are in consecutive order (DH12 to DH19) then you can simply do this in one go
Sheets("Source Ingredients").Range(Sheets("Data Entry").Range("A19").Value).Value = Sheets("Data Entry").Range("C19:C26").Value
Where A19 contains DH12 : DH19.
If A19, 20, 21 contain DH12, DH13, DH4 and etcetera (or any other order) then you will have to loop through those cells:
Dim Cl as Range
For Each Cl in Sheets("Data Entry").Range("A19:A26")
Sheets("Source Ingredients").Range(Cl.Value).Value = Cl.Offset(,2).Value 'This is two columns to the right of col A, so column C on the same row
Next