Put the ceramicīs in a bucket, buy the strongest acid you can get, normally here in sweden we have spiritvinegar or hydrokloric acid and mix with water, let the ceramic stay for a day or two to get rid of some calcium.
Most of your orkids want to grow in 6,5 PH or around.
Otherwise if it is to basic or acidic the nutritions dont work wery well.
Omex.co.uk has a acidity alkalinity test where they schow how nutritio works or do not work in different PH.
Thomas