I hear your frustration. Stick with it, you can be successful with plants.
Do a search on Green Water on this forum, you will find all the info you need on that particular problem. I will say that without a Diatom Filter, or a UV Sterilizer the solution is to fix the nutrient problems (see below) and have patience.
Your Ph and Kh to not match, that suggests something is buffering your Ph. This most likely makes it so you can not use the CO2 charts to figure your CO2. It sounds like you have a direct CO2 test. My Red Sea Master test kit has one. It always correlates well with the Ph/Kh/CO2 charts.
Most Kh kits have a starting color and a finish color. If your Kh is <1, then the test will go to the finish color on the first drop. Whether or not it is needed, you can safely add Baking Soda to buffer your Kh. 3 tsp at water change should be just about right for your tank.
Bottom line... You have High Light. You have CO2, but it is either too low or not diffusing well enough. You must fertilize constantly and consistently.
The new ladder you bought will not be adequate for a tank your size (sorry to have to tell you that). An easy method of diffusion is to run the CO2 bubble directly into a Power Head inlet. This will work very well on a larger tank like yours.
Your seachem macro ferts will not last you very long. They are expensive too. There is a cheap reliable alternative.
goto:
http://www.gregwatson.com/DryAquaticFertilizers.asp
and buy...
CSM+B Plantex or Tropica Plant Nutrition Liquid (TMG) or Flourish Comprehensive
Potassium Nitrate (KNO3)
Mono Potassium Phosphate (KH2P04)
Potassium Sulfate (K2S04)
Barr's GH Booster or Seachem's Equilibrium
This fert routine is widely used and prooven successful for tank your size. (125 Gallon)
1 1/2 tsp KNO3 or 13 tsp Seachem Nitrogen 3x a week (Sun, Tue, Thur)
1/8 tsp KH2P04 or 20 tsp Seachem Phosphorus 3x a week (Sun, Tue, Thur)
1/2-3/4 tsp K2S04 or 20 tsp Seachem P0tassium (only 8 tsp if also using KNO3) 3x a week (Sun, Tue, Thur)
½ tsp of Dry CSM+B or 3 tsp (30ml) of Liquid Trace 3x a week (Mon, Wed, Fri)
50% weekly water change on Sat or Sun
Yes, the Seachem macros are that weak by comparison to dry ferts.
The micro's and macro's on opposite days to keep certain elements from binding together and becoming unavailable to your plants.
Add the baking soda (3 tsp) and the GH booster (3 tsp) after the 50% water change.
There are many ways to be successful in planted aquariums. The things I am suggesting to you are a proven formula for growing plants and not growing algae in a high light CO2 injected tank. You can simply follow the formula, the pattern, until you understand more for yourself and then choose to experiemnt with other methods.
Fert Routine Ref:
http://www.barrreport.com/
Fert Lever Ref:
http://webpages.charter.net/zezmo/EI-DoseRoutine_v4_public.xls