YOu don't say whether it's in a pot or in the ground - if in the ground, what's the soil like? Skimmias do not like chalky soils, prefer neutral to acid - the yellowing of the leaves might mean they need a shot of sequestrene iron tonic, or similar iron tonic available there. Brown, black spots, sounds like leaf spot, can't tell if its bacterial or fungal without a photo. If fungal, you could try a fungicide, if bacterial, nothing you can do, spreads by water splash. Not real problems in themselves, but often indicate an underlying problem with the plant's health - in this case, perhaps chlorosis.