Guys should I continue using "Pro Complex Gainer" or should I start using "Gold Standard Whey Ptotein" ?

i'm a 24 year old guy, 5' 4" (166 cm) tall, after using pro complex gainer (PCG) for around 4 months i became 63 kg (139 lb) from 58 kg (128 lb), and my body fat % increased from 6.5 to 9.3%, i stoped using PCG around a week ago and continued working out, but my weight dropped to 61.5 kg (135.5 lb) and BF% is around 9% and i'm noticing some more fat around my stomach than was before.

so is PCG the reason behind the fat?
and should I return to Pro complex gainer or should i start using Gold Standard Whey Protein?
Guys should I continue using "Pro Complex Gainer" or should I start using "Gold Standard Whey Ptotein" ?
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