I have an allspice tree that was shipped from Arizona a few months ago.

I've been keeping it under grow lights 12 hours a day, humidity around 40%, and I keep the soil moist. It started killing off one of the larger branches so I cut that one back. Now the older leaves have a weird necrotic discoloration that ends up crispy and gray when the leaves fall off. The new growth seems unaffected. There are multiple new leaf buds growing very slowly.

Anyone have an idea of what this could be?