No no this is not bud rot my friend,
Are you still giving them calmag?
This can be due the over feeding with calmag.
So if you feed it give it a little less.
And maybe start giving it less nutrients. Because it looks like the leaves are burning up because they have to much nutes inside of them and to much heat and the LED is to close to the canopy!
Good luck my friend.
But 100% no bud rot don’t worry! She is just fine