If it's available, rockwool might be a better alternative. Jiffy tabs, at least in my experience, have a tendency to stay either too moist, or can completely dry out with little notice. With these extreme environments, it can be a coin-toss on whether or not the roots will thrive. I won't even use them for germinating/seedling stages anymore because of this. But maybe you'll have more luck with them than I did.

And I agree with SmokeNChoke...you shouldn't add much more than water & rooting hormone in the beginning. If you feel the need to throw in something else, one or two drops of Superthrive per gallon of water probably wouldn't hurt, but isn't really necessary.