I'm fairly new to photoshop (currently using CC 2015) so I apologise for any incorrect use of terminology and if I'm asking a stupid question.
I created an A6 document and followed instructions to create a watercolour texture background (via fill->pattern of a masked layer group) to paint on, but then it turned out I actually need the document to be A5; I've extended the canvas but the texture now doesn't cover the whole document. I found a make-do solution by duplicating the whole group and free transforming it to the new area on the canvas but I then can't blend the harsh line between the two (original and duplicated) watercolour painted layers - I'm happy with the A6 watercolour I had and don't want to paint anymore so am just copy-pasting to make the A5 I need. I tried starting again on A5 but the watercolour looks different so I obviously did something else with the pattern settings that I don't remember and can't replicate from scratch.
So essentially it boils down to: is there a way to simply just extend the existing pattern? Any help would be much appreciated and thank you in advance (: