Help! What is wrong with my toadstool

[StrombusEyes]

Hi all,
New reefer here. I've had my tank for about 2 months. I added this toadstool a few weeks ago - initially was happy for the first week, then withdrew its polyps and has been forever shedding since then.
I've also got a daisy coral (in background) that had the same issue - opened initially, now also clamped down
Other corals in my tank (a sinularia, 2x favia, open brain coral and morphs) are doing fine
My tank is an 100L all in one. I've got an A80 Kessil tuna blue light
Livestock - 1 clownfish and 1 fire goby, 2x trochus snail, 3x peppermint shrimp, 1x strombus snail

Parameters:
salinity 0.026
pH 8
Alk 8.3
Calcium 405
Mag 1380
Nitrate 5-10
Ammonia 0
Nitrite 0
Temp 24'C

Pulling my hair out trying to work out the issue! have been doing twice weekly 10% water changes...doesn't seem to make a difference

 

[Mr. Mojo Rising]

That kessil light is only 15 watts, unfortunately it will not grow anything. Your tank is 26 gallons, just to give you perspective, I have a 100 watt light on my 32 gallon, I have 55 watts on my 15 gallon. You need a light with more wattage. Leathers also love good amount of flow, without enough flow they flop over and can't stand straight. Personally if it was me I would add a 100 watt nicrew to the tank and then watch the corals grow.

 

[StrombusEyes]

That kessil light is only 15 watts, unfortunately it will not grow anything. Your tank is 26 gallons, just to give you perspective, I have a 100 watt light on my 32 gallon, I have 55 watts on my 15 gallon. You need a light with more wattage. Leathers also love good amount of flow, without enough flow they flop over and can't stand straight. Personally if it was me I would add a 100 watt nicrew to the tank and then watch the corals grow.

Thank you that is really helpful. I only kept the light on 30% intensity because I read that new corals don’t like too much light.
This also explains why I barely have any algae