Yeah bud, as the other folks said, PH that water to 6-6.5. Anything in that range is good for you. I grow in promix with a 6.1 ph. As for your watering schedule, let that soil DRY out before next drink. With seedlings, there's no need to drench the whole pot. Just around the seedling and no need for a lot of water, enough to moisten things up. Remember, it's a small plant, it has a small root system, for now. By the looks of the pics, it looks like she'll bounce back in no time, the new growth already looks great! That first true leaf is nothing i ever worry about, it usually dries up and dies on me as well, and thats with ph'd h2o. Its kind of like a food reserve for the seedling in its first week of life. Sometimes it dries out, sometimes not.