Under the gutter cover strips between the mounting points ?
At the very end small gutter covers there were actually visible gaps on the seam at each end where it goes from roof to boot surround as its a 90° angle as the factory sealant has went hard and shrunk \ become no longer bonded. I think they had been filled with green mossy looking stuff that had plugged them after it initially shurnk so wheen ive started a propper deeper clean ive unplugged them.
The boot hinge surrounds were the same, cleaned them as very green and mouldy with a detailers brush and soapy water and the sealant just started coming away.
Will probably just whip the rails and gutter covers off and run some sealant anyway as it seems the external factory sealant has past its serviceable life.