Plant Abuse Chart - 420 Magazine
Marijuana Plants Problems - Yellow Leaves, brown spots, nutrient shortage etc.
Cannabis Headquarters - Cannabis Plant Nutrient Deficiencies (with pictures)

I can Google too- you can find and cut/paste it, but I don't think you actually recognize it- this is NOT enough information to say 'you have an Mg deficiency'.
"my leaves tips are rolling down and some are canoeing,....Now some lower leaves are showing some discoloration....all of a sudden they look like crap,"

Leaf tips rolling down, canoeing. Could be excessive N or water, or rootbound.
Low leaf discoloration (discolortion NOT described any further as to WHAT color or pattern it shows). Could be overwater, aging in flower, insufficient light, nute lockout, N deficiency.
Plants look like crap. Could be they were eaten by the cat, thrown in the rubbish by Mom, tipped over, stepped on,....

Just illustrating- don't make a firm diagnosis on such shaky description. Those charts are only so helpful, when it's the CAUSE of the problem that is more important than what is specifically being locked out.
stinkyattic Reviewed by stinkyattic on . Help,leaf problems E-indoor or outdoor=indoor E-soil, soilless, coco, aero, or hydroponic=soil E-specific medium=promix and potting soil CSL-Soil type/brand HCL-Hydro/aero/soilless system type SCL-Anything you have added to the soil=worm castings,bat guono,perlite SCLR-Soil or slab runoff pH=7.0 E-Water source=was using tap water from a well,now spring water out of the bottle E-Source water pH=was 6.2 tap water,now 7.0 HRT-Source water EC (if hydro) Rating: 5