Could this also be due to the fact that I am only running 60 ppms? They got a little burnt on the edges before but could the spots be from a lack on nutrient like P or K. I went up 30 ppms today already so I know I want to increase slowly. How many times should I be changing out the res? I filled the water to the 3 gallon mark about an inch from the top. and the roots look nice. lots of new white ones.

Note: on the infected plant the top leaves are looking great with no spots at all. Is the plant taking nutrients from the old leaves to the new ones?