Zoas getting smaller and dont grow

[Revos]

Ok Hi guys plz help me out!!

So i have a 130ltr cube reef (55cm x55cm x45cm) with a 30ltr back sump. This setup is running about 4months This is an upgrade of my old 60ltr cube.

I have a tunze 9004, i run Carbon and gfo.
I keep salinity 1026
No3. 10
PO4 0,05
Kh 8
Ca 420
Mg1400
Temperature 26 celcius
I do 30ltr w/c per 15days and i replace carbon and gfo also.
For Flow i have 2 jebao rw4

I have a kessil a160we 20cm above the water line so 65cm above the sandbed!

I am running a 11 hours light schedule.
12:00 0%color 10%intensity
14:00 30 %color 50% intensity
14:30 15% color 50% intensity
21:00 0% color 50% intensity
23:30 0%color 0% intensity

I have some acans in the sandbed.
Some rock flower anemones, some ricordeas florida. 1 euphyllia 1 favia and many zoa frags.
Many trochus snails and 2 clown fish and 2 mythrax crabs.

Everything in tank is doing good exept zoas. The zoa polyps getting smaller They are open but they dont seems totally happy. They struggling to grow also. And they are much smaller since i get them. Some of them, some Days dont open at all.

I have dip them many times nothing Come off. No nudis, no zoa pox.

Sorry about the Long post and sorry about my english.
Any tips?

 

[nautical_nathaniel]

How stable are your parameters, do they fluctuate often?

 

[Revos]

My parameters are pretty stable. I Can keep them stable with the w/c.

I take mesurments weekly.
I use salifert tests and a tropic marin pro reef salt.

 

[nautical_nathaniel]

What is the flow like around the zoas?

 

[Revos]

I would say low to medium Flow.
I am running about 2000lt/hour with the jebaos and 1000lt/hour with the return pump.
The skirts of the zoas are small too if that helps. Do u think low Flow Can cause zoas getting smaller?

 

[reefpeeper]

What do u add to tank for nutrition?

 

[Revos]

About 2 months ago i start to add coral amino (brightwell)
I feed the fish every Day flakes and the corals once a week lps pellet (fauna marin) and reef Roids.
I also add microbacter (brightwell) weekly.

 

[Revos]

Any other suggestion guys?