Please Help Me Diagnose My Problem

Ive been slacking on the maintenance of my 4x4 hut grow for a week. Came in yesterday and checked the PH, it was down to 4.0.... ouch. So I changed the nute solution and Ph'd to 5.6. My ppm = 650. Not too many signs of problems except some slight spotting on some of the plants. The temp in the room has been a little hotter also(85F during day - 75F at night). Check out the brown spotting on some of the older leaves. My research tells me it is either a manganese toxicity caused by low PH, a Magnesium def or Toxic micro nutrient salt burn. Overall everything looks okay but I would love a second opinion. Thanks!

Doesn't look too bad. Should be okay unless you decide to slack off again...

Yeah plant looks good to me i would go with the acid being the problem... that ph got low and you got nute lock out simple as that.. from what i have seen man you got lucky considering you slacked for a week haha.. must have just recently started turning bad. anyway if you keep it ajusted an bufferd' up it should be just fine.