calcium def, does this work?

so ive been trying to diagnose my plant problem and have it down to calcium deficiency which i am pretty sure of,
i read somewhere that i can boil up some crushed eggshells then strain and use that water when cooled to water my plants and that will give them sufficient calcium.
does anyone know of any other way i could sort this?
ive been out looking for dolomite in a few places but doesnt seem readily available anywhere and im from england and we dont have walmart or homedepot b4 someone says try there.
is there anything else i could use my micro nutes dont have it in.

thanks in advance, any help would be great!!!
+rep for any ingenius sugestions

Well this wont 100% fix it, but it will help
1 table spoon Black Strap Molasses per gallon of water.
It has more than 1 good use, Im looking for the thread about it now, Ill post it if I can find it again.

Can you get your hands on some Bonticare Cal-Mag?