It's tough to compete with the "big boys" I use GH Flora Series. Three part; you can dial in the exact recipe per your application. for lettuce I use (1 part- FloraGro, 1 part FloraMicro and 1/2 part FloraBloom) I have found this readly available at several differant stores around town. You can use their on-line calculator as well. I started my seedling out around 500 ppm and will bump it up when I get my roots established. (I've had noticeable root growth in the last 72 hours)

Good Luck!

just dump about 2tsp of miracle grow and 1 tsp of epsom salts per gallon into your reservior to give the plants something to live on until you find what you're looking for.
I'm not suggesting this is the final formula you'll want to stick with but I personally have grown both basil and parsley with that formula for as long as I cared to tend to them. If nothing else it'll provide a band aid until you finish muddling through all the info out there.

Thank You