Purple Stems, tips brown and curled ???

As you can see from the pics the stems of my plants have turned a purple color. This same purple color shows up in the veins of the leaves. When new leaves are being produced they will almost immediately show signs of the brown curled tips. I read up on this and figured it would most likely be a magnesium deficiency(?). I'm running a bubbler system with my reservoir holding 13 gallons of nutrient solution. How many tsp of epsom salt should i add to make up for the deficiency?

Is there anything else I should be looking for that may be a problem as well??

Hi Kung
I usually put in 1/2 to 1 teaspoon per gallon of water, but it is usually only needed during flowering. What type of nutes are you useing? and how much? Is the PH ok? I use liquid karma for trace elements besides the normal organic nutes. If the nutes are over 1200 ppm i'd lower the nutes a little. let me know a little more and i'll try to help. Best of luck to you
peace
heart

I use the GH Flora series 3 part nutes. I use a 33% solution in the 13 gallon reservoir. The ph level is checked and adjusted daily. I dont have a ppm tester though. How much do those usually run? Also, if the nutrient solution gets too cold will that cause some problems as well??

the flora series contains an adequate amount of Mg,at 33% the solution is actually kind of weak,you can safely go a to 50%-2/3 of the recomended doseage,the res temp is good at 60-70fh,65-68 is ideal,my guess is also that the lighting is not strong enough either,the plants appear to show deficiencys of light and nutrients,good luck....bonbon

Get a TDS and PH meter, and add a 1/4 tbs per gl in your rez