That's an interesting mix of plants that you've selected there. A lot of those are going to get too big for a 10 gallon in a hurry, but right now I realize that's not your main concern.
Please understand that it's very common for Cryptocoryne species to "melt" as they go through the adjustment of being moved from one tank to another. While going through this melt, they'll look exactly as though they were dying. Also, the Echinodorus family of plants are often sold after having been grown emersed. They will also shed those emersed leaves as they develop new leaves better suited to life underwater. With that said, the two Hygrophila species are usually very easy to grow and definitely shouldn't be dying.
Lighting: You've got more than enough. That shouldn't be the problem.
CO2: Only 5 bubbles a minute? Do you have the bubbles going into the canister or where? Something is wrong with your kh/ph numbers. I don't see anyway that 5 bubbles a minute can produce numbers like that. How accurate are your test kits? I'd guess that you actually need quite a bit more CO2 than what you have right now, but your plants still shouldn't be dying. Not growing maybe, but not dying.
NO3: I don't know anything about Kent Nitrate supplement, but you do need a source of nitrate.
PO4: I don't believe your plants need any phosphate at this point. I doubt that's the problem.
If I had to guess, I'd say that a lot of your plants are simply adjusting to their new surroundings and that's what you are seeing. Most people recommend that you start out with fast growing stem plants in the beginning. They tend to be easier to grow, they're cheaper, and they help in the battle against algae. Crypts can be very finicky about any change in their surroundings.
You really should be getting more out of CO2. Check that to see if you can't up the output.
10 gallon tank |
2x15w GE Chroma 50 Flourescent Light
Flourite substrate mixed with a little bit of playsand
External Canister filter
DIY CO2 yeast mix in a liter bottle
Plants I have: