Rusty Leaves??

Hello,Can anyone tell me why im getting A sort of rusty red colour around the edges of older leaves??Thanks.

can you post a pic.It could be numerous problems we would have to see a pic and some more info like what stage of growth you are at what temp and humidity you are at .It may be a magnesium problem or calcium as i said would need more info and a pic if possible .be safe davey boy the postman.