What are these spots on my Spinach plants

[biloyp]

well it has been about 2-3 weeks since I started my DWC setup growing lettuce and spinach. Had some issues with High pH but got that resolved and that really helped with the growth. My air stones were floating and migrating to the same place. I fixed them so they would stay sunk and spread them out a bit. What a big difference, my plants loved that. I added a small amount of Hydrogen Peroxide and again I noticed some improvement in growth. But my spinach has spots on the leaves and I am not sure why. My pH is good, my TDS is around 1500 and water temp is staying around 75F. I am using fluorescent lights ( 4 T12 lamps). I was thinking it was a lack of nutrients but not sure. I took some pics hoping this would help determining what is wrong.