It is always very sad when you lose your cows, especially for you since you are just starting.
One or two observations
- If cow is not eating or drinking and is lame, my experience says it is ephemeral fever, another symptom is the viens under tongue become blueish.
In kannada its called (elle bandide).
We rub magnesium sulphate under the tongue every 4 hrs till it reduces. The biggest risk here for the cow is dehydration. Did the vets give glucose, and if they did, was it administered properly in the vein?
Secondly, I am not aware of vaccines causing such symptoms. Especially FMD vaccine if gone wrong, would cause FMD as chandra pointed out which has totally different symptoms.
I agree all point to bad vet services, sadly these experiences will help you to select proper doctors to use next time.
By my experience, I should warn you to be prepared as the future will have these cases anyhow as you are dealing with livestock.
Keep the faith and keep moving, dont let this deter your venture. This is just a speed hump.