[Frankie]

It's very possible it got wounded from the torch coral.
You said you are dosing Tech M every week but don't test for Mag. This is not a good idea. If you cannot test for it how do you know you need it? Remember most salts will provide you with what you need if you are doing regular water changes.
Lee knows her stuff and i would trust her over most. The links she provided are good ones. If there is a line under the wording it is a link. Good luck!