this does resemble mg def, but since the photos aren't real clear, it's hard to tell exactly. If you've given some epsom and there's no change, it might be another nute that is missing. In a situation like this I usually tell people to go get some Dynagro 7-9-5 fert at your local hydro shop. This fert can be used for either hydro or soil. Just follow the dosages on the back cover. 1/4 to 1/2 teaspoon for soil in a gallon of water. What's good about this fert is that is has pretty much all the nutes plants need, including calcium and mg. Don't over-fertilize however. Let the soil dry out quite a bit, then water with some fert in a gallon of water until water runs out the bottom of the pot. Then let it dry out some again to put oxygen in the root zone. Try this and see what happens.