Help ASAP !

This is the second thing I've ran into with my plant it's my first grow can anybody tell me what's wrong with my plant leaves ?

at a glance i'd say magnesium deficiency, but it would be helpful if you could tell us what medium you're growing in, what nutes you're using, temps, humidity, that kind of thing, and also a full plant picture

Looks like you may have a few nibble marks/holes as well ....unless that's from something else ....we need a full pic and info like mentioned above.