'Rust' Spots

Ok guys Im having an issue with what can only be described as rust spots on some leaves,it was on just my older plants but Im starting to see newer plants and growth being affected.I dont have any pics but anyone with any experience of this will know what I mean,it really does look like rust.
Thanks for any advice/replies.Peace!

calcium deficiency. feed botanicare cal/mag 5ml per gallon. damage won't repair, but it will prevent the issue on new growth.

Have you transplanted recently or made ANY changes.

We need to know about your
soil, nutes, feed schedule etc...

You might have to scap the hole thing. Clean the place up thoughly with something that kills everything. Unless you can totally sterilize anything from the grow, disgard it. Start again with new seeds. Soil is really suseptable to these sorts of problems. Never reuse soil.