White Patches on Live Rock

Hey there.

I have noticed that the top of my live rock has developed a bleach
white appearance on most surfaces. Looking around previous posts it
seems like this is a sign of dead coraline algae.

Should I be worried? The rock has turned white in all areas closest to
the lights that is not covered with algae.

I am new to sw aquariums. my first tank has recently finished cycling
and I added 10 hermit crabs and 1 turbo snail 2 days ago.

my 58g tank has t5 lights. 2x10,000k daylight and 2x420nm actinics. i
have been using the daylight lights only. 12 hours on/off.

i tested all the params today.

calcium 450 ppm
NH4 0.05 ppm
NO2 0.05 ppm
NO3 8 ppm

ph 8.2
alk 2.4
temp 82-84

I also have alot of algae growth in the last 5 days. mostly brown
stuff on the rocks, sand, and glass. other green and purple hair algae
has grown on the rocks only.

seems like all the params are where they should be. is it an effect of
too much light? or are these symptoms nothing too worry about??

Thanks for any advice you all have,

Aroon