What's happend ?

Hi When leaves get very dark its usually a sign of overdose, versus when they become very pale it's often lack of nutrients. But that rusty sort of colored spots and patches puts me most in mind of calcium and phosphorus deficiency. If you're giving the right nutrients then i would look into your ph, if its off, or in the wrong zone. I would definitely recommend recalibrating your ph pen also as they need it every month or so depending on how often its used. I had one go out and i thought the ph was correct and it caused total havoc on my plants leaves. Happy growing.✌️