Buggy 2D Lighting

I've made a new material to allow lighting on sprites in my 2D game which is using the default Sprites/Diffuse shader, and it was working fine, but recently it start acting weirdly.Its works ok in some places but near other light sources its very weird. I cant really show pics cause it won't show well, but basically the world is made of Tiles, and when the players light source is near another light source, the tiles lighting gets very block and doesn't degrade over distance, the near by tiles are very bright the next ones, not so much and then it goes dark. There is no fading.

I'm sorry i cant explain this, its very weird. Can anyone help?