Murky water - chemistry good

[esurfer]

Hi All, I've been maintaining a trouble free pool for over five years now thanks to this forum. However I have an issue I've never faced before. My pool is looking murky. I have a vinyl in ground pool @ 36,500 gal. My filter is a sand filter.
My chemistry is as follows, tested with the FAS-DPD (from Taylor K-2006)

FC: 4 ppm
CC: < .5
pH 7.2
CYA: 35
TA : 30 (really low I know)

A couple of things regarding my pool. I have a leak in my vinyl which normally requires me to fill the pool with city water every day, but with all the rain I haven't had to do that as often. (I'm in Missouri)
My sand filter usually runs at 20 psi and I will backwash when it goes up to 25 or more psi. I did back wash before I noticed it getting murky. Also, since I'm replacing my water on a regular basis, I run a chlorinator with trichlor to get the CYA levels up and then switch to bleach only. (12% Vertex)

Attached are pics of how it looks. it is usually crystal clear. Do I have an algae problem?
Thanks for the advice.

 

[mknauss]

Do a Overnight Chlorine Loss Test.
With your FC at 3 ppm or above, test your FC after the sun goes down, then again the next morning before the sun rises.

 

[esurfer]

There is definitely overnight chlorine loss. The water was looking a lot worse so i started the SLAM process last night. I added 8 gal of vertex, not knowing how fast it would be consumed, but it went down 5 ppm from what i can tell. So is that mustard algae or something else? Even with that amount of chlorine the water is still looking murky this morning.

 

[mknauss]

Follow the SLAM Process. You need to raise your FC to SLAM level multiple times per day. Read the article.