Fusionanswered grow question 5 years ago I wouldn't worry about it. Leaves will drop a bit as she creates her new leaves. Yellowing is is an emergency sign but if still green she's OK.
For the future soak your cubes for an hour in water 7.0 pH.
Then place your seeds in.
For next week just mist them once per day with water bottle. 1-2 squirts in enough. Watch your cube for drying out but at the seedling stage you don't need high temps so shouldn't be. Lower Temps stimulate the root growth.