I was thinking the same thing based on how dark the fan leaves were, but the rust spots and with the tips not being more burnt I’m thinking something else is going on as well.
What is your grow medium and feeding schedule looking like?
Well im watering them about every 3 days or so..when i do feed them its fox farm nutrients..about every other watering. I did see what looked like little fungas gnats i think in my indoor tent and was maybe thinking that's was the problem..but i think when i tried a little re-charge and flower fuel around the time i started to notice the dots on leaves. I have since changed the first few inches of medium and not added anything but ph'd water