They changed from ceramic wicking to all cotton Japanese cotton coil. They also made the wicking holes bigger so that it wicks better. There were a lot of complaints and fears that the ceramic material was harmful if inhaled. Kinda like little needles that stick in the lining of your lungs that can cause infections . You can read all about it on the aspire's website forum page.
I find the new coils a lot better in every way. Wicking, taste, and length of use. I always had trouble getting the ceramic coils to wick but since the change a drop on each wicking hole and two to three drops in the center, assemble tank, and let sit for 5 minutes and your back vaping in no time even with a 70/30 VG/PG mix. Sorry you not having any luck. Are they older coils you are using? You can tell by the size of the wicking holes. Are they authentic coils? Might want to check for authenticity. Maybe you just have gotten a bad batch. Try getting a replacement for them from the company you ordered from. Its worth a shot. Honestly though I have had zero trouble with mine. Good luck to you!