well. first. calcium isnt the kind of vitamin definicent he is talknig about. in addition to supplamenting with calcium, you also need to dust with multivitamin, so the animals get all the other vitamins they need, not just calcium. things like vitamin a, and d. if youre not providing
uvb, and you dont have calcium with d3, the gecko isnt going to properly absorb its calcium. if you dont gutload your feeders with fruit/veggies then theyre going to have deficiency problems with other vitamins.
is your vet a specialist? did he look at the eye? sometimes leos will get things stuck in their eyes, like grains of sand, and they need to be washed out, if nothing is in the eye, then it could be a vitamin defiencency.
as far as selling you things out of date, i would tkae them back to the vet office and demand a refund. i WOULD suggest you get a fecal, but check around other vet offices, to see if you can get one cheaper. 36 pounds is like what, closer to 60$ us? thats obscene. a fecal is a relatively simple thing, you take poop, stain it with a chemical, and then look at it under a microscope, and even then, its only going to show you things like internal parasites, if it has something like crypto it wouldnt show up.
not saying that your animal has crypto, if your other animals are fine, and you havent exposed them to any new animals, or new used cage furnature, then it should be find, my point is that you shouldnt need to pay more then 25$ for a fecal. check around different vet offices, usually you dont even need an appointment to see the vet just to have a fecal done, and if you live near a vet school, sometimes you can have them done by students for even less.
and if it WAS a vitamin issue, then it wouldnt show up in a fecal stain either. really, it sounds like your vet doesnt know what it is. and... he is just looking to rip you off.
good luck.