Deficiency Question

Hi all, long time lurker first time poster.

I am having what I think is a Magnesium deficiency 33 days into flower but since this is my second grow I would like someone else to see what I am seeing.

Rundown of my setup
4x4x7 Tent
430cfm fan pulling air out through a cooltube
1000w iPower Ballast with Eye Hortilux Super HPS bulb (Switch out for MH during veg)
4 plants in 7 Gallon Smart Pots 40%ish Super Soil topped with Roots organics (Added suconat/bud candy on day 25 flower)
Dehumidifier keeps humidity solid at 50%
Temps 72night 79-81day

So here is the issue that I noticed about 2 days ago my fan leaves are beginning to droop/curl downwards slightly and I have began to see brown spots showing up on some fan leaves of 1 plant.

Here is a pic of the spotting issue.


Here are some bud shots of my Nirvana Chrystal



Here are some pics of my tent
Front left is a bagseed from my Father in laws outdoor bud the rest in the tent are Nirvana Chrystal

In the second pic you can see the leaves bending down on the back right plant which is also the one having the spotting issues.

Ha well I see I should have checked the forums after work I see there is another thread started a couple hours ago with my same issue >_<

Edit: Seeing as the other guy only made his worse any tips would be appreciated otherwise I have some GoBox Calmg I will add to my watering tomorrow.

I think on the other thread he just ended up making sure to pH his water cuz he was getting a slight lockout. Yours may b the same, I would suggest pH the water and see how they look in a couple days. If they r still looking bad then try the calmag or some Epsom salts. Hope this helps

Thanks for the advice I will take a look at the PH tonight after a trip to wally world for some strips