"Ade" wrote in message
A very weird appearance on the soil in some pots. Very large blobs
of clear
jelly just sitting on the surface of the soil. Definitely not water
retaining gel.

Are you sure it couldn't be water retaining gel? I've had the same
thing you have described happen in a pot in which there has been a
rose which has been there for some years. The gel only appeared a
couple of years after the rose went in and after a period of extended
heavy rain. The gel seemed to heave up out of the soil.