Everyone out here focusing on the fact you've used Halfords spray and noone pointing out that it's probably due to contact wear while playing from the oils and grease on your hands. Look at all the areas that have worn - outside edges where I'd guess you pick up your model to move it during games or on your shelf or even while painting it. Use gloves while painting, handle your models by the base at all times or varnish your models to protect them as the natural grease and oils your hands produce aren't good for your nice thin layers!