I dont think its the peptide itself; I dont think it would matter which GHRP you used, Hex, Ipa, GHRP2 ect... GHRPs give you a gh pulse of your bodies natural gh reserves in your pituitary gland. Certain things in us will block your bodies gh pulse; even if its synthetic gh you just injected. Carbs and Fat will block your bodies natural gh pulse which is why when dosing GHRPs/CJCs or even HGH for that matter we want to inject when our bodies are in a fasted state.
You do not want to eat fat or carbs a minimum of 30mins before or after injecting as they will blunt your pulse. Which is why on the day you fast (I fast) I usually inject at least 4 times because I know I'm burning pure fat on those days.
You also want to load up on protien as you bodies metabolism will devour the protien and this meal will keep your metabolism up.