Something doesn’t look quite rite. @MattyBear @Covertgrower & @dbrn32 will be of good help I’m sure. Good luck and I know these folks can help u out. 
I don’t really feel like she’s screaming for help. Biggest thing is keeping from overwatering at this point. If she stretching try lowering light a little.
she looks over-watered,
r u letting the cube dry between waterings.?
how close and what kinda light is on her.?
any fert’s yet.?
pH of nutrient solution.?
I only sprayed the small cube once in a week with a spray bottle. Then yesterday leaves were already that white color I soaked the bigger cube with very small amount of seedling nutrients then shook the water out before putting in the smaller plug
if u want good help, we need good info of the grow.!
a single pic and little info is not going to get quality advice.
there is a 98% chance that u r doing something wrong to cause the yellowing,
does not sound like she is over-watered, but can not be sure…
without providing info and pics u r wasting your/our time.
Very sorry to WASTE your time I’m new at this didnt really know what info you needed that’s why I asked instead of typing an entire paragraph each time I gave a question. I have a king plus 1200w led 24” above canopy, temp is 75F, ph when I soaked the large cube with a very small amount of seedling (bergmans) nutrients was 5.86ph. Humidity is 58% in the dome, don’t really know what or how many pictures of the single plant would help and the leaves are more white not yellow
u r probably getting ‘hot’ spots thru the clear dome’s lid,
the light is (probably) bleaching the leaves.!
cut a thin white T-shirt or bed sheet and place a single layer over the lid,
watch the sprout closely, if it starts to stretch move the light closer,
in a few days when she is ready for no dome, move the light up and adjust it down as she can handle it or if she is stretching.!
dome ‘hot spots’ can also be remedied by raising the light to 4 feet above the dome,
most of us do not have that kinda head room.!
unfortunately, the paragraphs r a necessary evil.!!
we don’t want to read em anymore then u want to type em, but everyone here desperately wants everyone to do good.!!!
as far as pics go, repetitive pics do no good, different angles of the plant and pots/containers and grow room/equipment pics help tremendously.!
Your not wasting our time mate.
If you think you might ask for help later, might consider copying and saving all the basic information. Then all you have to do is copy n paste.
good lick
@Fluffy the first round leaves do eventually fall off. So as long as the secondary set is doing alright she will pull through. I’m not seeing anything that’s looking serious, so just be sure to keep an eye on her.
Do you plan on transplanting to soil or hydro?
You can transplant at this time, as there are no nutrients in the rock wool. If she’s going in soil just place a water bottle cut in half over her to keep humidity up.
If she’s going in hydro be sure to remember to top feed until her roots make it to the water.
I was just curious didn’t see that on my first seeds. Yes it’s going into hydro when I soaked the larger piece of rockwool I did put about 1/4 the recommended amount of bergmans seedling nutrients in the water. The unit I’m putting this single plant does not have a top feed so I’m going to be watering it myself. I just need to keep it moist maybe add alittle water every other day?
As long as you stay vigilant and hand water until the roots reach the water, you’ll be fine. @Fluffy