Have black spots and craters in diamond brite

Last week I noticed what appeared to be black dirt on the bottom of the pool. But it would not vacuum or brush away. Upon closer inspection, It appeared to be little spots of (what I'll call) algae. It was very dark green, almost black. And they were in small craters in the diamond brite all over the pool. I tested the water, and found that my SWG was dirty and had not been producing chlorine, I was at 0 chlorine. The pool store told me it was black algae. I got the SWG working and boosted for 48 hrs, got it up to a 5 where it has been for a few days. Continuing to scrub with a metal brush, but they are stubborn.

Now they have diminished by half, but they are still there. Was told to add black algaecide (from leslie's). Added the recommended amount, but still no change. Is this really algae? The diamond brite is not even a year old (done last July) and now it has all these small craters. Any ideas or suggestions would be great.

THanks

Post a complete set of current water testing numbers so someone here can better advise you. Welcome!

When the spots were first noticed the water was a bit neglected:

Chlorine (SWG not working) was at 0 (not sure for how long)
Stabilizer was at 30
Phospates were at 1000
ph was ok

Following the pool store advice (before finding this forum), I got the SWG fixed and boosted for 72 hrs. Added 4 lbs of stabilizer, 4 capfuls of Phosfree, and half a bottle of Black Algaecide (not all at the same time). I also began scrubbing the spots twice a day for about a week with a wire brush.

Now, as a result, have the following numbers:

Chlorine is maxing out on my tester at 5, and has been there for a few days now.
PH is perfect, only demanding a little acid to keep in check
Stablizier is at 100
PHospates are at 0

The spots look 100% better than they did, but they are still visible to me. More greyish than black now, but still remnants in the little craters they seem to have formed. I continue to scrub by hand while diving, but just cant seem to get them all out.

I assume this was black algae spots, Is there something more I can do? Should I have not added the copper algaecide? What next? I really want to get rid of all of it. Any suggestions would be great.