I would step off the nutes completely for a little bit longer. When they're youngin's they don't need any, especially since you're using quality soil. Then once you do start to use nutes, I would start with 1/4 the recommended dosage, and slowly up it from there to prevent nute burn. If you notice the tips of your leaves turning yellow or brown, and heat isn't an issue, you should scale back on the nutes then as well.