Help :-( can't figure it out...

[Jakef150]

My tank -2 yrs running, bio cube 29, skimmer tune 9002,AI SOL

I change water 5gal every weekend

Today, I filled a litte SW from my tank to bucket and put 2 rocks in it while I was little clean up in rear (not sand) and also catch chrmois.

Then put rocks in and fill the tal SW water up.

Approx 2 hours later, starfish died and few LPS release some kind of white web like melting shrink...

What the heck happen??

SPS looks fine to me

Do starfish cause this?

I just changed brs rox carbon to re fresh. 2 tbsp in a mesh bag.

I tested- Alk 8.6, cal 430, 1026, ph 7.8, slifert nitrate .02, phosphor 0.02 Hanna checker

Help

Thanks
Jake

 

[Hydronic]

Was the bucket used for something else before this? Maybe somebody used it for chemicals/water solution for washing floors or something?