Hi, I'm new to all this but on my system all my plants including my tomato plant were staying alive but not much more when my PH was high. Before I found out my pump had a metal core my PH was running 8.2 to 8.4 As far as I know your optimal PH should be 6.8 to 7.0, since I got mine down to that level all my plants are starting to green up and grow.

What are your readings? Where's your Nitrates level at? Tomatoes need a lot of Nitrates. What has changed from your past to your present readings?