Camellia with leaves turning brown

Hello....newbie gardener and a bit worried about my beautiful camellia! Planted it in feb/march, it has flowered beautifully, but now the flowers have finished and the leaves are going a muddy brown sort of colour - not brown and crispy but just discoured and a bit sick looking. I have got heavy clay soil, but I put some mulch etc under when I . Planted it - could it just be a bit waterlogged with all this rain?