Magnesium def.?

Came home today after being gone for a few days and found problems on one of my plants. Its bottom leafs are yellow(Some almost completly white) and then some of the middle leafs have yellowing tips as well as little reddish brown spots. I thinks its Mg but I just wanted a second opinoin before I start making it worse than it already is. Thanks

Yea I read that before I posted and now that I read it again Im 99.99% sure. I just have a nasty tendency of becoming a weed hypochondriac so once I start reading those guides by the time Im done I ask myself "why even try growing this when clearly my plant has a deficeincy of every nutrient known to man?" and tell myself "I am a terrible person cause I feed my face yet my plant is in desperate need of calcium, nitrogen, Phosphorus, and every other element in the periodic chart".