Corals dying for a month from Temp swing?

About a month ago my temp dropped from its 78-80 norm down to 70 overnight. I turned return pump off and forgot to turn back on after feeding and found the temp at 70 in the morning.

Over the last month i have had many different sps start to recede slowly and rtn randomly. I lost 5 to 10 sm colonies. It still hasnt stopped, i found one rtning this morning. They will recede slowly for a while and then just be gone overnight. I had a couple just RTN without even receding first. All at random times throught the last month.

Is this the normal amount of damage to my reef from a temp swing? Or can something else be at play here? This is the first time i had a major temp swing so its really had me wondering. Weeks after the swing fully healthy and extended colonies just rtn?

 

I wouldn't chalk that up to the temp swing. I know a SPS grower locally here who lets his tank make that swing every night. In fact he believes it increases growth. If they were going to be affected by it they would have shown damage must faster than over a months period. What are all your params?

 

just checked my params,

Calcium 400
Magnesium 1230
Alk 10
ph 7.9-8.1

I started raising mag.

Could it be the low mag?