You might try CLR using the plastic bag trick. Or take remove the entire faucet to do it, which is pretty easy.
We get calcium buildup on the outlet of all our faucets regularly due to the calcium level in our well water. CLR works good on it but sometimes I find I need to scrape the heavy buildup off with a knife first.
If you have a washerless/ceramic cartridge in the faucet, maybe that's plugged up. I know sediment in water can plug them up, and I think calcium might too. If you have a cartridge and it is plugged up, you have to replace the whole cartridge.
If it's an on-going problem, it might help to get a filter of some sort. Calcium can't be filtered out though. A Camco exterior inline filter may or may not work for sediment for you as they are only 100 microns. They have low flow rate at 1 gpm and as the filter plugs up, it will really slow down. We use a dual 50/5 micron filter on our house and am just about to install 60 and 5 micron "whole house" sediment filters in series in our TT good for 10 gpm. If your water quality is often not that great, I would consider a 10" (tall) filter cartridge and housing if you have space. The cartridges and housings are quite inexpensive if you get them online or at a plumbing wholesaler.
Oops, missed your last post.