yellowing of leaves. my only baby left is it ok?

Here is a picture of the only one left of 5 from my dwc setup. Either ph or bad tap water killed the rest. put it into a new 5 gallon DWC system a day ago. Now looks like this:
ph: 6.0
temps: 77 F
light: 400w mh 3 feet away
humidity: 40%
distilled water, no nutrients
10 days after germed seeds planted.




I know the cotelydon leaves are supposed to die, but this early? and the tips of new growths are just the slightest yellow. What should I do?

looks like perfectly normal growth for a seedling, the seed leaves somtimes die off early. just keep an eye on it.