No I haven't but seedlings like a higher pH around 6.5 to 6.8 in seedling/veg stage in soil. Then in flower lower pH to 6.2 or close. Also most common problems with seedlings is damaged roots, poor watering practices, heat, and wrong kind of light. Double check all these especially poor watering practices. Soil needs to dry out before giving more water. Roots need oxygen if kept wet u deprived soil oxygen. One last thing is I use roots organic soil for seedlings never had a problem.