If you have limited ability and no tools to effect change then I would suggest that you contact Seat Leon suspension specialists and not those who supplied or fitted your kit and pick their brains over your ride height discrepancy. Your suspicion about the wrong spring rate is where I would check out first. Years ago long before you were born it was not unusual for those who wished to lower their cars’ ride height to cut the springs down as a cheap way of doing so.. Going back to the original supply or fitting will result in the same answer every time.Just prepare for the sucking in of air between teeth though from some and don’t let on you have limited knowledge or they will try to talk you into all sorts of expense.