My two pups are 6 months old now and eat only half (1 cup twice a day for each pup) of what they use to eat (2 cups twice a day for each pup). They are very active and have lot of energy. Is this normal?

Yes, totally normal. By 6 months old the biggest growth is over, and most puppies will scale back their food by half or even more.
Two cups total per day, per dog, is about right for most adult goldens.

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Gibson's Golden Girl, CD, CGC, TDI (born 3-20-1997), a.k.a. "Tiny"

CH Rosewood Little Giant, UDX VER RA SH MXP MJP VCX WCX CCA CGC FFX-OG (born 3-10-2007), also UCH HR UUD UJJ URO1 UHIT a.k.a. "Tito" (the Tito Monster)

and my heart dog
Gibson's Golden Guy, CD, CGC, TDI ( 01-31-1998 - 01-02-2012) a.k.a. "Toby", "HRH"

LOl Barb - try telling that to Rose and my DH! Yesterday I informed my DH that Rose is completely on adult food now and she needs only one cup on each of the two feedings - since she does get fruits, veggies and cheese as treats and he looked as pitiful as the dog. When I said no more food, Rose put her ears down and DH put his head down. I had to threaten him with all sorts of medical terms some of which I literally made up to convince him that it is not good for Rose.