I think you're safe.
The browning is from the tip of the leaf and that is usually nute burn or sometimes heat.
With early budrot, you will normally see 1 or 2 leaves start to go yellow and then droop and if you pull on them they come off easily and can often see a bit of the fungus on the petiole/stalk of the leaf.
If you catch it then, you can just chop that bud off before it spreads, but will need to keep a close eye.