They look pretty much normal to me. The bottom leaves die when it's hungry as they use the stored enrgy in the bottom leaves to fuel the new growth for the top leaves. I'd up the nutes just a bit the next res change. Go a little less than 3/4 speed and see how they do. Do you have a PH and PPM meter? You also need to cover those net pot or algae will get started. You can use covers you can buy from sunleaves or make them out of styro plates. Cut a circle out of the plate bigger than the net pot, put a 1" hole the the middle, cut from the outside edge to the center hole and slip it over the hydrotron.
What strain is that or is it bagseed? What's your set-up like?
I use the Flora series nutes also.