Hey man your setup looks very similar to mine!
I also built in a recirculating and aeroponic mister feature into my DWC. I personally found both to be useless, especially after the roots have hit the res water, they are submerged so the extra water up top is meaningless to the plant. Plus, the pump heats up the water, generally a bad thing. Make sure your air pump is solid though, thats very important
As for the leaves, the yellowing was prolly nitro deficiency. You really dont want to cut ANY leaves unless they are infected or over 50% dead. Even yellowing leaves can produce food for the plant.