I have noticed one of the seven stars over the ladst 4 or 5 tears has really dimmed prior to this I don't recall it being so dim is there an explanation for this? or has it always been so; & only recently I've noticed.

Its probably you.

maybe light pollution has affected the sky. are you sure it's only one of them?

some of them are double (and more) star systems. so these variantions are normal

Yes it's only one of them if you look at the plough & Imagine it as a saucepan with a bent handle as I did when I was little; the top of the saucepan which would be the star on the left is only just visible I feel sure when I was little the luminosity of all the stars of the plough were fairly equal...It's probably of little interest or consequence to most but I was just curious & wondered if any else had noticed this too...