Nuiscence Coralline Growth on Scrubber

[Aeros]

Over the past five or so cleanings (weeks) I have noticed a steadily increasing patch of Coralline algae growth forming on my scrubber mesh. It began in a bottom corner and is now prevalent along the entire bottom half of the screen. Normally, I'm fairly pleased to see Coralline algae popping up (except on the display tank glass) as a sign of a healthy reef. The problem however, in the areas on the screen with coralline growth there is no green algae.

I use a three layered screen, and vigorously scrape down to the plastic mesh and fresh water rinse thoroughly (using warm tap with the dish sprayer) at each weekly cleaning.

What started as a small patch is slowly taking over my screen. I fear at this rate I will be growing a coralline algae filter soon.

Has anyone else experienced this? Is it a possible cause of underfeeding the tank? Too much additives?

Tank stats:
55g reef (too much LR)
crappy skimmer that barely pulls a cup a week
feeding 3x a day plus. Mostly frozen carnivore mix, spirulina, and frozen cyclopeez.

Bio load:

Yellow tang
Six line
Hippo tang
Coral Beauty
Yellow clown goby (son of a bitch eats acro - reef safe my ass)
Large yellow headed spits sand all over goby

3x Pacific cleaner shrimp
1x Caribbean peppermint shrimp

8x hermits
About a thousand nerite? snails (little but plentiful)

Algae scrubber in custom made light box with 3x 2700k CFL floods. Approx screen size 7x8" double sided. Approx flow rate 700 GPH.

I dose liquid calcium reactor, or purple up weekly as well as essential elements and a splash of iodine when not using purple up.

Tank nutrients all read 0
CAl - ~400
Alk - ~8
Ph - 8-8.3 (daily cycle)

[SantaMonica]

Lighting. Not enough in those areas. Point the bulbs there, or replace the bulbs.

[Broder]

What is the wattage of the lamps?

[Aeros]

Three 23Watt CFL outdoor floods (nice for my use because of the flat glass/diffuser face). http://www.amazon.com/DIMMABLE-FLOODLIGHT-COMPACT-FLUORESCENT-OUTDOOR/dp/B001DBLIMY

[SantaMonica]

You can use cheaper ones if you want; you need to replace every 3 months anyway, even if they look perfectly bright (they are not).

[Aeros]

I just used that as a quick reference. I am using a cheap-o brand from Menards (on sale too). They're all made by the same Co. in China and just re-branded and sold here for whatever mark-up people are willing to pay. I like these for the reduced light leak around the edge.

I mark all bulbs with their start-up date and cycle them out after ~3 months. These are only ~2 months; and one is near new.

On the next cleaning cycle I'll get some good shots I can post here to illustrate the issue.

I have fantastic growth elsewhere on the screen. All of it real thick GHA, that is also a real bitch to scrape off.

Sunday the 30th is the next scheduled cleaning.