I have my light bulbs 10cm high, and also had a similar amout of watts per gallon in my tank (96w/20g). I followed the recommendations of reducing the light and that helped dealing with algae (a 24w bulb was removed and now I work with 72w).

Another point is the quality of light, besides the quantity. You mentioned your tank is running for 8 months. Have you replaced the bulbs in this period?

That is another point I came accross one week ago. My tank is running for more or less 8 months as well. As soon as I replaced the bulbs, plants responded readly. Specially glossostigma, which probably was suffering the most with a higher water column absorbing the poor quality light from old bulbs.

Regards,
Evandro.