Hair Algae

Merry Christmas to all..... I have a planted 55 gallon tank with C02 system w/ ph regulator. I have a fully planted tank and it is doing very well. Plants have doubled in size and have excellent color. However I am having a bit of a problem with green hair algae. I keep my lights (2.3 wpg) on for 8 hrs and have my ph at 7. I am adding ferts once a week (only half a dose). I can't remember the name of ferts but it is a liquid that has a type of measuring chamber on one side. It was highly recommended and seems to be doing a great job. Why would I have this algae if the plants seem to be growing so well. I would think there would be no nutrients left for algae. Its not a big problem and can be manually removed. Would lowering ph by increasing C02 help? I am going to add some Discus at a later date. I have about 13 neons in tank along with some cories and a bristlenose which doesn't go close to the Algae. This algae only seems to be on certian plants. Any suggestions would be appreciated.

Thanks