It could be you overfertilized or it could be you are watering too often. Or both.
You should only water when the pots are actually dry and feel light weight. Once a week maybe at this stage, the most common mistake people make is watering every day or every other day when it doesn't need it. That drowns the plants.
They probably don't even need nutrients for a few weeks. Just ph'd clean water.
BTW those look like they are going to be MONSTER plants when they take off. What are they? The leaves are HUGE. Looks like really good genetics.