the leafs look like they burned. tThe soil has a lot of mineral/salt deposits. What is the quality of your water? What do you use for fertilizer? The pots need to be elevated to let the water drain away from the soil.

As Susanne wrote, your tree has leaf tip burn caused by high soluble salts in the root zone. You can easily wash out the damaging salts by flushing the root zone with clear water. Salt build up in a container comes from the water used and the fertilizer applied. One question - is your water attached to a soft water system? If so not good for your trees.

Check for spider mites which cause cupping of the younger leaves...I would. Or wash them off thoroughly with warm water under the leaves especially as you flush your mix out with fresh water at least once a month..You will probably find those leaves so brittle, they will easily fall off once you touch them.