First, stop doing the water changes. For non-CO2 tanks water changes mean fluctuations in CO2 content, and that tends to induce algae to start growing. You should be able to get Vals, especially, to grow without much trouble. Just dose about half the EI quantities and only once a week. For a ten gallon tank, your 18 watts of light is low light intensity, and probably alright for non-CO2 and non-light demanding plants. Everything will happen slowly with that kind of tank.

Is the algae growing on the leaf edges black or green? Growing on the tank walls sounds like green dust algae. If it is that you could attack it by wiping down the walls and changing most of the water every day for several days in a row. It is hard to get rid of no matter how you try to do it. The other method is to ignore it for 3 weeks, let it grow until it changes color and thins out, indicating that it is at the end of its life cycle. Then wipe it all off, change most of the water and repeat the wipe down and water change every day for a few days. At worst, this would leave you with a lesser amount of algae to deal with. I found when I did this the plants thrived as the algae hid everything from view, so it was rewarding to finally wipe it off and see the results. But, that was with a higher light intensity too.

But, once you get that GDA under control, then stop doing the regular water changes. Just top off the water when evaporation losses require it.