Fight, Start over, Give up
 

Well I didn't understand why some growers change the nut. once a week and why some just top off? I didn't understand that growing hydro was harder with organic nut. I had six different fish tank heater short out and stop working, not good for ebb and flow and temps in the greenhouse down to 40F at night and 82 every day w/ sun. I was using Hydrogen peroxide but not enough w/ 75 gal tanks. I was warned about used equipment and I washed the tanks and trays and net pots w/ hot water and bleach, I didn't understand I needed to let them soak. The lettuce tray was the first but tomato tray and now the pea tray are showing sign of root rot, I':(m sure I was the cause of cross contamination. The trays were covered w/ panda film to keep out light but maybe not enough air movement in roots?
My main question is this worth fighting to save the tomato plant and pea plants, roots just showing black tips, not like lettuce all black/brown. Or should I move every thing out and just start over, may be w/ salts, after I bleach every thing including floor? Or may be give up on ebb and flow and go drip?

Hello gardenmark,
It sounds like you have had a lot of problems. I'm not sure if they are all questions though. Something is wrong if 6 fish tank heaters burned out, there must be a electrical problem. Or they are getting damaged somewhere. Used equipment shouldn't be a problem as long as you clean and sanitize it thoroughly. Scrub it thoroughly with soapy water, then mix some bleach and water (about 1/3 bleach) in a spray bottle, and spray the entire system numerous times. Also soak all the tubing and connectors that you can in a bleach water solution overnight. Soak the pump in hydrogen peroxide (so bleach wont decay o-rings etc. parts). Clean and sanitize the greenhouse with the bleach-water spray the best you can.

The roots should be able to get air, or they suffocate. I cant see how bad things are, so I don't really know your situation. But I probably would start over. there is a product that might help, but I have never tried it so I don't really know if it works. but here's an option: Pythoff: Hydroponic nutrient conditioner

Personally I would go with a drip system for tomato's, probably peas depending on the setup, and a water culture system for the lettuce. But that's just my preferences.

Looking and smelling better
 

I rinsed the trays ,pumps, tanks, and plants w/ H2O2 29% and water , And I already have new white roots. I keep flushing w/ H2O2 and adding 1/2 cup per tank every other day. This morning the musty bad smell was gone. Not only that but I had a swarm of wasps and ladybugs and I haven't seen an aphid in several days. Also I have good new growth on almost every plant except one tomato plant.:)

Root Pix
 

Yes it would help to see pix o the problem, the pix are from the lettuce except the last two are the tomato tray. Thanks for the help