Need a little help

My plants have been growing steadily for a bit now with no problems until a few days ago. I noticed a few things going on with them. First, every one of my plants has started to grow this green fungus like junk in the soil. Its easy to see cause I'm using 2 liter bottles cut in half and they are the clear plastic. Most are just starting to get it, but this one has really got it good. I'll attach a pic of it, but I'm using a crappy camera and the resolution ain't so hot. It probably won't show up too well.

In the 2 pics below I'm trying to show how the leaves and stems have turned purple on two plants. I was trying to trouble shoot this problem from the facs link that is stickied, and I'm thinking Potasium deficiency. Am I right about this? Or could it Phosphorus? The leaves also feel brittle and rough to the touch.

I have only done 2 waterings using a 5-1-1 liquid fish fertilizer. PH of my water is 6.3 - 6.5 and am using Black Gold potting soil. Its been around 3 weeks since I germinated the smaller guys. About a week and a half longer for the bigger one (Had some stretching issues with the big one).

Some pics.

Also getting some brown / dead spots on a few leaf tips and edges.

That is algea.. not a big problem.. from to much water. cover the top of soil with computer paper. You should not use clear plastic.

transplant them.. bigger (not clear)

Yah, I've been doing alot of should nots lately. Thanks for the heads up. I was planning on moving them to bigger pots in the next day or 2. I'm gonna miss seeing them roots grow though.. lol.