No it’s is fine. They do vary over time. If the water has a fresh aroma, tastes good and has a good mouth feel, it is working. I do advise customers though to give their amphoras a sun bath on a really baking hot sunny day as it expand the clay and helps with porosity.
Empty the amphora of water, clean the outside (I like Soapnuts and Scrubby for this) then place is in the sunny position. You can put a piece of cloth over the top to stop anything falling in. Make sure it can’t get knocked over by the wind or animals.Leave it out turning it a bit a few times through the daay, so the sun strikes all the sides. You could even lay it on its side to blitz the base too. It really does wonders for the amphora!