a little unhealthy

so i'm onto my second grow, and one of my plants has some leaves that are looking good, but have little burnt spots it looks like, or more like small rusty spots in the middle of the leaf. these are for leaves nearer to the bottom, not the whole plant and it isn't affecting all that much of the plant, but i'm wondering what it might be,,ideas?

my first guess would be lockout of a particular nute like Ca from an off balance ph. what is your ph and growing setup?

using soil. haven't checked pH in a while i'll do it next watering, i'm just using that paper stuff that gives you a general reading like around 6. it's been between 6 and 7 everytime i've measured thus far...also the soil i'm using has slow release nutes 4 weeks so i haven't been giving them any nutes, well small dosages sometimes

last grow i had a Mg Cal deficiency so i put a tablespoon of dolomite lime in each container...

I would add the lime again. you really should at the minimum pick up a cheap ph aquarium tester at walmart for like 10.00. much more accurate and your water should be close to 7. not less than 6.5.

so the soil has nutes, you use staright water not ph'd so this will happen