Are you wicks clean? If not, you can disassemble to expose the wick and coils, remove flavor wicks and then rinse under running water. I then generally dry burn and put in new flavor wicks. Or just replace the head. I've had PT heads gunk in as little as two days with some juices. But yeah, you can thin juice with a few drops of distilled water. And (on most devices a tighter draw) pulls thru a thicker liquid.
**Edit**
Oh, that Vash is fast!