Algae Or Not

Hi all

Am fairly new to aquariums. Had my tank set up 9 months now.
I really like the live plants and have tried to add as many as is practical for me to maintain. Currently 9 live plants, supporting 22 small community fish in a 100L tropical. However, I've noticed that there are brown specks and spots on most of the broad leafed plants. Is this algae? If so,what can I do to get rid of it on the leaves its currently on and what can I do to stop it returning?If not, what is it?

Some backgroud on the tank

• I have a basic 27W flourescent bulb, which is on a timer for 6 hours per day, often they get a few extra hours if I'm in the house.
• No fancy CO2 injection or anything. Simple airstone and a filter with venturi bubble outlet.
• Water stats are Ammonia 0, Nitrite 0, Nitrate 10-30% (about 10 immediately after cleaning, to about 30 by cleaning day) . Weekly 30% change.
• From the photo, you will see I have tried to pick plants with low light requirements as I know my lighting isn't great.
• I'm happy with the growth rate, as they all grow green and strong, but not too rapidly. I wouldn't really want them to grow more quickly
• I do have to scrape the glass weekly for algae growth, and also the large decor gets scubbe wth a nailbrush monthly to remove brown buildup.
• The fish are always grazing on the plants.
• I have had some issues with fish flicking, which I'm not sure if this is connected to the browning plants.

Even with blowing the pic up, I can't see the spots. Can you take a close up of just an affected leaf?