i am not seasoned at all lol but i just finished reading about this it looks like sulfur deficency or ph. it looks like one of my own so thought i would let you know. i may be wrong so do some more reading, but thats what i think and ur ph is?
I would have to agree with jetski, when a plant has too much nutrients the nutrients build as a salt compound, the "salt" than keeps the plant from accessing necessary nutrients, which can cause yellowing curling of leafs rust colored spots on the leafs and many other things. The tan and brown is the nutrient overdose showing, most people call it nutrient burn, it causes the plants leafs to turn brownish tan and start flaking away. anyways to wrap this up do what jetski said, he gave you the correct answer. your plants might look a little limp and sad after flushing the soil but they will perk up afterwards. good luck!