Hey dude, based on the photos it is certainly plausible that this is heat stress. If you’ve already moved up the light then this issue may rectify itself shortly. It’s often a common symptom of root issues too like binding or overwatering. She’s in a 5gal so binding is unlikely at this point. If you find that the medium is always moist when you’re watering then try letting it dry out a little longer. Other than that, think you’ve probably diagnosed your issue already👍. Good luck