Major problems in reef tank. Is this fungus?

[xdcbenoitxd]

So I did a tank upgrade a few months back and my tank is again going through the very ugly stages. Last weekend I left for 4 days. Before I left I added a few snails and one small button coral that had been quarantined in another tank for a month. Upon my return I found a few dead snails and all my corals look very angry. I tested my water and realized my dKH had shot up to 12.2 so I've temporarily stopped dosing and am doing several water changes. I have a rusty algae that we I'd as diatoms but they are not going away it's been a couple months. (Maybe something else?) I also noticed this white stuff all over my tank and sump. Is it fungus? Or precipitation? I swapped out my purit carbon and my water parameters are as follows:

pH (not an average just at time of sample) 7.9
dKH 12.2
Nitrate 0.0 (trying to bring it up but do have a decent amount of hair algae so obviously there's some food in there)
Phosphate 0.02
Magnesium 1320
Calcium 430
S.G. 1.026

I use the following products in my tank:
Tropic marin all for reef (daily)
Purit carbon
Tropic marin bacto balance (just swapped from elimi-np as my nitrates tanked)
Aquaforest pro bio s (weekly)
Aquaforest pro bio f (weekly)
A wide assortment of fish foods and algae
Red sea AB+
Coral amino

Current livestock
3 Hammer coral
3 types of zoas
Xenia
Waving anthelia
Frogspawn
Duncan
Green star polyp
1 Picture wrasse
1 Gladiator clownfish
1 pajama cardinal
1 yellow watchman goby
A limited number of assorted snails
Assorted hitchhikers

Any advice or opinions would be greatly appreciated as I don't want to lose more livestock.
The first picture is the bottom of my sump. The second my GSP.

 

[xdcbenoitxd]

So my snails have been dying because I seem to have dinoflagellates. I am getting something for the treatment and know it's harmful towards invertebrates (pulling out all cuc and corals into QT they go) but what about the fish?