While powdery film appearing on tiles when rub them with your hands

Hi
The tiles in shower in our ensuite seem to have a white dusting film on them that appears if you rub the tiles with you hands. See attached pic

It seems to rub off if you rub it with a dry cloth

The shower tiles are sprayed each time we use it with one of those daily shower sprays out of Aldi/Tesco and about every couple of weeks we wash the tiles and the shower like a deep clean

Whats this white residue/powder. Its not grouting as its a few years sinced the bathroom was done up

Any thoughts re how to get rid of this and keep it away or is it just dried out soap/shower gel/daily shower spray residue and just needs to wash the tiles regular in warm soapy water

Thoughts
Thanks