I wouldn't be as it could be a number of factors, full stomach? The environment they're in? Take for instance I went to a festival only a one dayer with my mate and 2 birds and we had defqons and a variety of dids the girls halved a MasterCard (don't worry was an OG one saved, took a right pick n mix down some pills over a year old) then anyway they halved a defqon and one was saying she hadn't come up and was taking ages and was from the 1st run of them and exactly the same as the ones me and my mate were munching, anyway we all had a balloon each (this an hour after she had the half) and then BAM!!! She came up hard!!! She went under having a panic attack almost but it was because it all of a sudden kicked in, but they were from the same batch as the ones we all had been having. Basically saying it could be their metabolism, took longer to break down as there was more binding agent and also I do feel the environment you're in, a delay can be any number of reasons, maybe the MD was in bigger chunks in it so took longer to break down I duno, I could and probably an chatting pure shit as I am chsrged up haha, but just saying everyone is different, some come up after 20 mins some an hour and they could have taken the same Gary from the same batch.