I have two pine trees I bought around Christmas a few years ago and l keep them in pots. This year I moved them and now they get late afternoon sun, morning shade. I noticed recently that the leaves are turning brown and look like dying. But I also watered a lot lately thinking they were dry. Did I over water it? Or maybe it’s getting too much late afternoon sun?
Your trees have damage on the side facing the sun. You've successfully grown them in containers for a couple of years, which is good, but the move exposing them to harsh afternoon sun has not agreed with them. Conifers grown in containers have limited root space compared with trees in the ground whose roots are surrounded by insulating soil . It's important to have sufficiently large pots to maintain enough moisture to keep the trees and their roots cool and functioning properly. Planting them in the full force of the afternoon sun is hard on them. You might want to consider a shade cloth screen to protect them.
To keep conifers happy in containers plant them in appropriately sized pots with well-draining potting soil. Because the pots are surrounded by air, they reflect air temperature, both heating up in summer and freezing in winter. It's better to have them in partial shade where they don't experience severe temperature changes. Soil in pots is prone to drying out. Trees in pots need regular and deep watering. In really hot weather they may need watering once a day, or even more. An annual fertilization with organic or other slow release fertilizer will keep them growing well. Refresh the pot's soil by removing the dry top soil each spring and replace it with compost-enriched soil. This article has additional information, Growing Trees in Containers