Smokwirianswered grow question 5 years ago Don't worry my friend, you have near to perfect temperature.
Your ph is also just perfect, the soil is a bit wet, if it still is, wait for the soil to get a bit dry before the next watering. (push your finger into the soil and feel if the soil is still wet, if it is, wait with watering.
the problem probably relies on overwatering, which caused in this stage can be described as very mild damage, which you spotted just on time.
heat stress does look the same at early stages, but your temps are perfect