Me too but some times you have to pull her pants down and look at her roots.... that is the only way to see exactly what is going on. Color, root bound, root can get heat stressed also. take a peek will answer a lot of questions.
80 deg
Gently and as carefully as possible pull the plant and look at the roots. If they are brown, soft and a little slimy you got problems. If they are white, firm and healthy looking you have ruled that out.
When a healthy plane goes down that fast I look and check roots first.
When it happens that fast your roots died. they sufficated , I garentee you that if you pull the plant and look at the roots they are all Brown and soft. should be white and ferm heathy looking. now what caused it???
I call it Growing pains. The center of the leaf grows to fast for the sides to keep up. I too was thinking what am I lacking or bad happning? when just give it time to mature. If you know everthing is good? it can be too good! LOL