Plaster Repair, and stain removal while draining pool

[optikon]

I'm in the process of draining my pool per the recommendations in this previous thread: New pool owner really high CYA and CH what should I do

Draining the pool has made me realize that the "weird spots" on the stairs are plaster damage that will spread if I don't repair them. Is this something that I can fix myself or should I call in a plaster company to fix it?
View attachment 60732
There are two spots like this on the stairs that I would want to repair.

Additionally I have some staining around a couple of my return jets, and gray staining all over the pool. Any advice on what it is and how to remove it?
View attachment 60734
Thanks,

Ryan

 

[pooldv]

My guess is calcium scale. Is it raised and rough?

More here, Pool School - Calcium Scaling
And here, Pool School - Pool Stains

 

[optikon]

My guess is calcium scale. Is it raised and rough?

More here, Pool School - Calcium Scaling
And here, Pool School - Pool Stains

It is actually very smooth, I'm not sure if it's raised, in fact it may be slightly lower. I tried a spot acid wash with 50/50 water and muriatic acid, then brushed it. That didn't really do anything to the stain.

 

[pooldv]

Ok, we'll need to see some test results then on that. The last few sets of test results would be best.