Eagersanswered grow question 5 years ago Yes pretty sure it is heat stress, new grower here also hit with a heatwave whilst in windowsill. Could have a feel of the medium? Mine was very warm when carrying water then roasted in sun. Left medium cooking the roots!
It will stunt the growth a bit but possibly make sure it doesnt get the intense sun on the pot during the day.
At least thats what happened to me, had to deal with stunted growth but it should bounce back.
Good luck, hope the grow goes well 👍