Way too young for nutrients. Flush now (regardless of tapwater ph) and don't resume fertilizing till the 3rd or 4th set of true leaves.
Ingoing ph should be in the 6.3 to 6.8ish range. You can check online for your local municipal water quality report, which should give you the water ph for your area, what they use to chlorinate it, and other handy facts...Even if you are on your own well, local water reports are available.

Did you get a soil probe, or a ph pen? (soil probes are worthless)

Water seedlings when they need it, but do not let the pots (cups) completely dry out, nor should you keep them sopping wet. Once a day should be fine in cups that size. Possibly less. If the cups feel empty when you pick 'em up, it's past time to water. :thumbsup:

Personally, I'm not a big fan of the 24/0 light schedule. I've tried a few different times with various strains, none performed as well as when on 18/6.