concrete like substance on gunite pool

I have a 41k gunite pool 2 years old. I use a SWCG, have a DE filter, nature 2 fusion soft which I don't use the metals cartridge at all.

Pool was closed with all levels of water fine. Water level was dropped.

We opened pool to see lots of sandy like substance all over the bottom (2nd opening and first time we saw this). Additionally there are spots that appear like hard concrete formed on the gunite. In our cozy corner, our swim out and on the bottom of the deep end. The spots feel just like concrete. I can't rub them out and was thinking of using sandpaper but really wanted to know what they were and what the best way to rid them was?

Pool was opened with water being pretty clear other than the sandy substance. There is no place I can imagine this sand came from.

Additionally we are always fighting pH levels which I understand is somewhat normal but honeslty I go through muriatic acid by the gallon weekly or dry acid (not sure why but I did find the pool pH dropped faster using dry acid than just muriatic acid from Lowes).

Our water is very soft so that's our other big cost so we do have to add hardness after every rain fall.

Current reading
FAC = 4
TAC = 4
pH = 7.6
TA = 90
CYA = 50
Hardness = 250
Salt = 3100
Phosphates = 100

The pool company wants our FAC at only .5-1 but honestly we had issues when we were that low. They also want our CYA up to 60-90.

Any ideas on this concrete substance or comments on pH or suggestions on water chemistry?

I've gotten no responses. I' can't attach photos but here is a link to them http://s746.photobucket.com/user/mag...ottom_concrete

Now to add insult to injury there is a 2foot vertical crack that I noticed in the deep end wall today while brushing the pool.

We had all our chemical levels perfect upon close, the pool company did all my opennings and closings. Not sure what they added.

The pool is only 2 years old and we have always had issues with the acidity. We have gone through huge amounts of dry acid and muriatic acid trying to keep pH levels down. We have brushed the pool weekly (2x a day in the beginning).

Just looks like you have thin plaster, which has eroded, and exposed the underlying gunite. Unless you've had some major acid-washing going on, or have kept the pH below 7.2, that's an installation failure. A shell crack, after only 2 years, is absolutely an installation failure.

Didn't see any "sandy substance" in your pics, so I won't speculate there.

FC less than 1.0 with CYA > 60 ppm is an recipe for absolute failure. Read the Best Guess Chlorine page, linked in my signature, and then get a K2006 (Amazon link also in my signature).

Thanks pooldoc.
The last pictures show the underlying concrete coming through is what it does look like.

We've never acid washed the pool....

I've informed poolco regarding the crack. I have not heard back.

What would be the way to correct the crack? From past history poolco wouldn't even pressure test lines after their consultant left the pool deadheaded.... yes they replaced pipes by filter that blew and motor but I've felt there was a small leak always that possibly was underground. Could the crack be a result of the pipes leaking under ground causing ground erosion?

How would you proceed if this was your pool? What would you at a minimum expect the poolco to do for you?