Brown Spots, Red stems, yellowing lower leaves HELP

So my plant is about 3 weeks in to flowering and so far everything had been going well i have just been using tap water and it seemed to work. I started to notice yellowing arount the edges of the leaves and someone suggested magnesium def. so i bought some molasses (grandmas, Robust. 8% magnesium) and added 1 Tbsp. to a gallon of distilled H2O I have watered with this 2 times now. I use 2 2700K, 26W CFLs(i know i need more light, and i is on the way) besides the molasses, i have not added anything to the cheap soil i am using. About 2 days ago i noticed Brown spots all over the third set of leaves and a little on the 4th set. the first two sets of leaves are yellowing and dying (perhaps normal for third week of flowering?) The new growth looks healthy. The Bud looks good Is this a nitruent deficiency? or something else? I have ordered some 2-7-7 fert that i am hoping will solve my problems. Today i plan to buy some Cal/Mag, and some worm castings. Does anybody have any advice for using these along with 2-7-7 cactus fert to make my baby healthy again:-/ here are some pictures of what i am describing.

That 2nd pic is nute burn. Time to Flush!

Roseman said:

That 2nd pic is nute burn. Time to Flush!

Click to expand...

could it be from Molasses?! if not is i OK to flush with a tablespoon of molasses in my gallon of water... or does that kind of defeat the purpose of flushing?

because i have not added fertilizer in a long time, and when i did it was a very small amount one time only.

I Appreciate the help.. HTB.

If you only added nutes once your entire grow and you are growing in soil without time release fert-
I would add some fert. What you have should work.