Plants Slowly Dying. Should I try Phosphate?

[tackful]

I have a 29 gal tank with 55 watts of light, 3 months old with 24 small fish, mostly tetras. My plants are Java Fern, Wysteria, Annubias, and something tall with large leaves that I was told was easy to grow. None of these are doing well; the Annubias is turning black and the tall one is showing brown spots on its leaves. I have been dosing Potassium for two weeks, and trace minerals plus Iron for one week. This hasn't helped the plants and has caused a dark green algae to appear on rocks and driftwood.
Should I consider dosing Nitrogen and Phosphate? I've heard that they can cause algae, but those are the only supplements I haven't tried.
The LFS (Aqauforest in SF) recommended adding Aquasoil to my substrate to lower my pH from 7.2 to 6.8, which they think might help. If I do, I think I'd want to tear down the tank in order to place the Aquasoil under my large size gravel substrate, which has a look I'd like to keep. Any advice on this?
Thanks for the help. Tackful

[phanmc]

If you're not dosing nitrogen and phosphates, you're starving your plants of essential nutrients and no amounts of potassium or micros will help.

Start dosing all nutrients and carbon as well, either through CO2 or Flourish Excel.

Regarding algae and the use of nitrates and phosphates, I overdose on both regularly and have no algae issue. Conversely, I've seen many people have algae issues like blue-green algae when they are low on nitrates.

Best way to fight algae is to have alot of healthy plants, starving your plants of nutrients isn't a good way to fight algae.

[Mgamer20o0]

PNK plus traces. its worth a try. get some dry ferts. saves you lots of money.

http://www.bestaquariumregulator.com/

[tackful]

Went out and got a supplement with Nitrogen and Phosphate today. I'm convinced. Thanks for the help. Tackful