I am pretty new to this plant stuff but I'm encountering a little bit of a problem with my mint and other herbs (and sunflowers). I know for a fact I have four-lined plant bugs nibbling my mints and apparently its just a matter of waiting them out. However, I've been noticing some black spots on my mint and sunflowers! I'm not sure what the cause is but I was wondering if anyone had any insight and whether or not there's a natural treatment for it. I raise my herbs to feed my pet rabbit (and for tea for myself!) so I would really like to treat everything as naturally as possible. I have used Sevin dust on them once before I realized it was bad news but I have not used it since. To my understanding, everything should be okay since I only used it once and dusted lightly - it was many waterings ago.
Anywho, here is a picture of the damage. Sorry for the poor quality! This damage takes place in no specific areas, it is not secluded to the top, middle, or bottom parts of my plants. It also is not heavy damage, there's not a lot of it. I've been plucking the leaves with said damage on them so the plant will grow in healthy foliage.

Does anyone know what this could possibly be? Is it just normal stuff or possibly from the FLPB that have been a nuisance? As you can see, a lot of the foliage is perfectly fine. It is only a handful of leaves that show up like this.
Any insight would be wonderful! (: My dad wants to throw the chemicals at it but I'd like to take a natural approach since rabbits are so sensitive and it is being grown for him first and foremost.