In my experience, light will be the most important thing for your vals (the old rule of thumb is 2-3 watts/gallon). I'd avoid root tabs since cichlids dig, and unlike sword plants (which will never survive the hardness of a Rift Lake tank), vals aren't heavy root feeders. A liquid fertilizer definitely won't hurt, but you can get away without it. In fact, you don't even need to supplement CO2 with vals (they are able to utilize carbonate in lieu of carbon dioxide for photosynthesis). I wouldn't worry too much about the melt, these are very hardy and resilient plants, it will just take a little bit for them to get used to your water parameters. You may lose some (especially toward the corners where your tank looks pretty dark), but once the rest establish themselves, they'll send out runners and you'll have more plants.
