Avocado leaves dying and dropping off

Jesse111 starts with ...
Hey guys, wondering if someone can help. Have had this tree for about 6 weeks now. We've had it in a pot the whole time, and have moved it a couple of times trying to get best sun/shade spot.

About a week ago we noticed leaves going brown and dropping off. It started with only the oldest leaves, but has since claimed some of the new growth. I measured pH at about 6.5. I think it may have to do with excessive salts, as i put rooster booster in the soil, but wondering if anyone can confirm/give any ideas.

Cheers

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