How do I possibly have a algae?

Hi guys I’m having a hair algae problem so here’s some tank info

20gallon tall
Coralife T5HO with Ati aqua blue plus and blue special on for 10 hours a day
Controlled by a reef keeper at 78.0 degrees
Some cheap’o powerhead
Hob filter for Rox 0.8 carbon and gfo reactor
Hob filter chaeto reactor with 10k and actinic led strip on 24/7
20lbs live rock and 20 lbs Live sand
I use frits RPM salt and 0tds RO/DI water

I do a religious 5 gallon (~25%) water change EVERY Sunday and vacuum the sand every time very thoroughly. I also dust of the rocks and clean the glass every time prior to changing

My feeding schedule had been so stingy the last 2 months that unfortunately I’ve lost a couple shrimp ☹️ I feed LRS Reef frenzy and they love it

My tank inhabitants include a YW Goby a red fire fish and a royal gramma. 1 cleaner shrimp, 1 peppermint shrimp. And various corals from softies to LPS and some monitporas and 4 snails and ~10 hermits

My tank just hit 1 year on the first!!! 😃

Cal, mag, and alk are all in check pH rides at perfect 8.4 no ammonia or nitrite.

I test no nitrates or phosphates but I know that’s because the algae is consuming them.

My chaeto does not seem to grow yet the hair algae is running rampid

I’ve scrubbed all the rocks a few times during water change in the bucket but the aglae is back in a week

I use to run No3Po4X but I stopped about 4 months ago due to a clear slime forming

I guess my question is how and where are the nutrients coming from to feed the aglae?
And how is it outcompeting all the other implementations I’ve attempted to stop it?

I’m completely stumped and all advice and help will be appreciated. Thank you for taking the time to read and help in advance!!!