Howdy,
The suggestion with plant substrate is a good one, I used laterite when I set up my tank. You can also purchase clay balls, which you insert near the roots. That saves you from emptying out your tank to fertilize the substrate.
The pH can only be lowered by peat within a low range. What's your current pH value? As stated by Vitaliy, the angels are probably fine.
I feel very strongly about CO2. I consider it a perfect waste of money. I had a professional grade CO2 system by Dupla on my 80 gal tank, and the plants really didn't notice a difference. CO2 makes a difference only for a few plant species, e.g. Cabomba.
You mentioned the lighting. That's cruical. What lights do you have, and how old are the bulbs?
HarleyK
ps
You might want to check out the plant subforum