Well the purple stems could be normal. Some strains are like that. Low temps can cause that too. Its really the least of your worries. It could be a phosphorus def, but epsom and/or molasses is not the answer to that. Epsom is a source of magnesium and calcium not phosphorus. The fox farms shoiuld have plenty of phosphorus if your Ph is good so that your plant can use it.
If you want to use the molasses you should know exactly why and how first.
I found this in the organics forum by Ohsogreen >
"First use only unsulphured molasses, like Briar Rabbit or Grandma's Molasses (brands). Mix one ounce ( 1 TBLS) to one gallon of chlorine free water. If you only have tap water, let it set for two days & 99% of the chlorine will evaporate. Then you can add the molasses.
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You should bubble (oxygenate) it using a cheap aquarium pump & air stone for at least one day. Or just pour it from one clean container (jug or bucket) to another a couple of times a day, for at least two days.
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This provides extra oxygen to the good micro-beaties, they then eat, mutiply, & kill off - the not so nice micro-beaties. The longer you oygenate this mix, the more good guys you end up with. Their eating & pooping out the NPK (bioconversion) is what make it highly soluble. Over time their bioconversion reduces the N and pumps up the P & K slightly. Not a big shift, just a point or two.
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This makes a good growth stage fertilizer (that's cheap).
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Just mix it light the first time & water in lightly - like one quart per plant.
Start low & build slow. This prevents overfertilizing.
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Use this mix one week & plain water the next.
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You can add nutes to the mix, but remember your adding to a mix with a NPK of about 5-1-3 already"
Growing MJ requires a LOT a patients. Keep in mind that it could take several days to see the results of somthing you do to try to affect the health of your plants. Inexperienced growers ALWAYS try to do too much. lemme know how they're doing later in the week. Are the tops still green? Are they pushing out hairs? Hang it there man!