For filter I have one Ehiem Professional II 2028 with surface
extractor. The filter contains Black Diamond carbon on the bottom
tray, the ceramic tubes on the second, and the course rock on the top
along with the sponge seperators. I also added some floss under the
first stage before the water goes through the carbon.

If you are injecting CO2, then you should consider more lighting. About 1
watt per gallon in a non-injected tank is ok, and 2-4 watts per gallon in an
injected tank.

IME, as plants grow in, and lamps age, more lighting may be needed than was
initially the case when the tank is first set up. So, initially your 80
watts might have been minimally enough light. Now, it may not be.

I am not sure how much Flourish you are adding. Are you checking your iron
levels? There are test kits available that can give you a rough idea of how
much iron is in the water. I use this level as a guide to whether I need to
add more "micronutrient" fertilizer (i.e., Flourish or Tropica Master Grow)
or not. With a relatively low light level, I would be surprised if you need
to add Flourish three times a week. If your iron is around .1 ppm, then you
need not add fertilizer. If you have a lot more than this, then you are
probably overdosing. (Seachem makes a good iron test kit.)

Change your water more often, and change more of it. If you have not
discovered the python, this is a beautiful tool. It makes water changes
much easier. I would change 40 to 50 percent of your tank water once per
week.

The sheet algae you mention sounds like blue-green slime algae, which is
actually a bacteria. If it is indeed blue green algae, it normally rubs off
of your plants and tank equipment quite easily. Typically, this type of
algae kinda smells bad too. Erythromycin and other antibiotics can treat
it, though if you do not get your light and nutrient mix correct it will
return. Many claim that low nitrate levels cause blue-green algae to
appear. In the case of low nitrate levels, the blue green algae tends to
form on the filter return or somewhere that gets air easily. (I understand
that this type of bacteria can extract nitrogen from the air directly, and
so tends to favor locations where this can happen more easily.) I always
recommend Chuck Gadd's site, lots of very good and accessible articles there
to help you understand everything from CO2 injection to fertilizing your
plants. Check it out: http://www.csd.net/~cgadd/aqua/. He has an article
there about plant nutrients that you should read. He also has an article
about dosing your tank with nitrate should it need it. (With the amount of
water you are changing and the frequency that you are changing it, I find it
hard to believe that you have a shortage of nitrates. Low nitrates are not
the only reason blue green algae can appear, but that is a scenario I am
familiar with. Other readers may be able to help me understand the
circumstances under which blue-green algae occurs.)

Also, I would take the carbon out of the filter. Certain important trace
elements that you are trying to maintain (by adding Flourish) may well get
partially or entirely absorbed by the carbon, especially just after you put
new carbon in. I would get rid of the carbon in favor of some of the
ceramic loops that Eheim sells. You are really just trying to create a
hospitable place for nitrifying bacteria to live. The other filter
substrate Eheim sells is probably better for a planted tank, since it
accomplishes this without taking out trace elements.