What does my avocado suffer from

I've had salt and root issues with my avocado trees. Leaching did the trick for me. I would water about half it's normal amount, twice as much. So higher frequency, lower water volume. Regular pruning also helps the tree circulate nutrients more efficiently. Hope this helps! You're catching it early it seems, so shouldn't be hard to correct. Look into Anthracnose as well, although I don't think you've got fungus starting, it would be good to go over the symptoms if your plant starts getting worse. Good luck!

4 reasons it could be: Salt Accumulation Avocado Root Rot Iron Deficiency Anthracnose

it looks like bad watering habit to me, some peppers which i tried to grow indoors and with low natural sun were showing this necrosis signs, roots were the issue in mines that time. Too moist, no dry/wet/dry/wet cycle