I pretty much do mine the same exact way as the OP, but have better results. Mine almost always root in 4-6 days, and I've only lost one so far, and I've done 75 or so.(in veg) Hmm.....Let me go copy/paste a explanation i typed earlier, explaining how i use the jiffy pellets, because that could be your problem.
I'll be right back.
""I also use jiffy pellets, and didn't have much luck with them at first, and had quite a few die. Here's what i do now, with excellent results.....After I expand the pellets with water, I give them a good squeeze to get alot of the water out. Then I roll them between my hands, squeezing them, which breaks up the peat. You don't really have to do this part, but i'm a freakling perfectionist, so i do it anyway.LOL......I then take a nail and break up the chunks of peat inside the pellet, so it's nice and fluffy. Then I gently form it back into it's original shape, and poke a hole in it with the nail, in the center. Make the hole so that it doesn't go all the way to the bottom of the pellet, and it's a little bigger around than the clipping you plan to use.
Now here's the most important part, and the part where I was making the mistake.....Make sure that after you insert the clipping into the pellet, that you give it a nice firm squeeze, forming it around the clone, making sure that it's making good firm contact with the entire length of the clipping.
That, is what makes them root well.""
Other than that, my temperatures are high, between 80* and 85* all the time. One more thing....I never keep the pellets really wet. After I wet them the first time, i only give them a light mist with a spray bottle, once a day. Being too wet can slow them down alot, so that could be your problem.
EDIT: I've used both the cloning gel, and the powder, with the same results.