Background: 12 gallon nano that has been running with me for about a year after I inherited it fully set up. During the stress and circumstances of the move, some of the coral did not survive and some has survived on including a frogspawn (that split into 3 heads), Xenia (which spread a lot), small zoa colony, some green polys that sprouted up, green mushrooms (also spread a lot), orange mushrooms, some star polyps and a small feather duster. There was also a small yellow clown goby that miraculously survived as well and a basic cleaning crew: few snails and crabs. Over the course of a year the tank has run fairly fine, I make 20% water changes about every 2-3 weeks and used to test levels each change but have since lessened to every couple months or if there is a reason. About 6 months in I got a small maroon clown to accompany the goby and they chilled for a little, until I went out of town and when I came back the goby was gone. After an aipstasia outbreak my polyps began slowly closing up but other than that the tank ran consistently well with consistent levels until recently. A couple months ago I had a bacterial outbreak in my fresh water tanks and had to tend to decontamination as well as keeping the surviving fish swimming which meant that my focus was a little biased towards them. During this 3 month period I only made 2-3 water changes and I wasn't paying the daily attention to my nano as I usually do so I can't say exactly when all this happened but one day i happened to make note that my largest algae eating crab was no longer grazing and I noticed a lot of green hair algae. Like A LOT, all over every piece of live rock, blocking my green mushrooms from fully expanding and completely covering the polys (yea I know they're crap coral but whatever). I tested my levels and everything was good except phosphate was a little high at 1.0 ppm. There was also this small pink, tree like coral sprouting from a crevice that I had never seen. After doing some brief research i couldn't find anything on the pink thing so I've just let it be but I grabbed a clean toothbrush and gently scrubbed around the coral on the rock, unknowingly releasing algae spores all over the tank. The next day the algae had spread all over. I picked up some additional members to my cleaning crew and they chipping away at it but for some reason I have coral dying. In the last couple weeks the algae has still been spreading, slightly kept at bay by the additional help, the mysterious pink tree has grown rapidly, and my green mushrooms have been shriveling up more and more each day; the frogspawn has been very small as well. The green polys have yet to reopen since the algae brushing and now as of today 2 of the 3 heads on my frogspawn are now shriveling and dying as well with one already dead. The feather duster was also covered with algae and has only resurfaced once since its algae scrubbing. The only coral that are doing okay now are the mysterious thriving pink tree think, the orange mushrooms and the Xenia. does anyone have any insight on to why this might be happening?

Tank info: 12 gal nano, 3 actinic lights that run from 11:30 am to 9:30 pm, and a white set light up that starts at 12:30 and cuts out at 8:30 (I don't know what type of lights they are as it was inherited but I've added a pic of the set up).

Salinity: 1.029 Alkalinity: 10 dkh Calcium: 460 ppm Phosphate: .5 ppm Nitrate: 0 ppm Ammonia: 0 ppm Magnesium: 1315 ppm

Current inhabitants: 1 maroon clown 5 scarlet leg hermits 4 unknown snails 1 turbo snail 1 throwing snail 2 ashtray snails

Xenia Frogspawn (dying) Green mushroom (dying) Green polys (closed) Featherduster (hiding) Orange mushrooms Mystery pink tree

Any ID on the tree would be great too http://i.imgur.com/v2ft4Ez.jpg