Apparently there was an update that makes Mystery Candies stop spawning during the Sugar Crush part of a level. It's now extremely difficult to get three stars (750k points) on this level. I've gotten three stars on every level up to this point, but even with crazy cascades the most points I've earned on this level is 650k (~100 tries). The level is wholly dependent on mystery candies generating color bombs, stripes, etc., and for this reason it doesn't make a difference how many boosters you use, the score will remain mostly the same.
Because of this mechanic change, I think the score requirements should be lowered. Of course, if anyone knows some trick that I may not, I'd also be open to hearing it.