White Water Mold (I think)

[JohnTDOT]

Hello I just came upon a new problem that I have never had before. My indoor pool looks to be full of white water mold. Im not sure how this happened. Its a large indoor pool that uses CO2 and liquid chlorine. The only thing that I did differently than usual was manually added muriatic acid. My CO2 tank was empty and I had to wait until the next day for a refill. I added about 6L of muriatic acid in a 120,000 gallon pool to lower the PH as it was about 7.6-7.7. about 6 hours later I started to see the white water mold. I super chlorinated and vacuumed the pool. It isn't as bad but there is some left. What should I try next? Also do you think adding the acid was the cause or just a coincidence?
The pool levels are currently
Chlorine 2.5
PH 7.5
Alkalinity 100
calcium hardness 150

[Teapot1]

Hmm, tricky without pictures etc. Does it look like broken up tissue paper?

I can't fathom a reason the muratic acid would cause white water mold but could it have been there stuck in with some limescale or be limescale that the lowering of the pH with muratic acid has released. Did you pour into one spot or distribute the acid around the pool? Would be handy to know a bit more of your chemistry with total alkalinity and calcium hardness. Are you using salt chlorination, do you use CYA stabiliser?