I'm actually disappointed at my searches for Calcium deficiency remedies as all I am finding is speculation, with no solutions! I do know this. Lime, eggshells, limestone, etc. won't work. My soil is high in Ca. The problem is it's not available to the plant in these forms. Bone meal is mostly this way too - but sometimes there are other forms of Ca in it that may be absorbed better. Epson salts have no Ca, but again as stated above may help make CA available or be transported, and you may have Mg issues too? Though some sites state that too much Mg can make Ca less available! Milk - not sure on the Ca part - probably not enough in it as a spray? But it's perfectly OK to spray on plants. I've used it for powdery mildew and it worked on some plants and did not on others, but no ill effects. I watered it down = about 1:4 milk to water. I don't have the perfect answer, even sites where speculation is not the main way of communication, there seems no great answers. I will try Calcium chloride (I have some bulk form for pickle making and brewing), and Epson salts and see. I'm not even sure the problem is Ca deficiency with my plants!