Help, my system seem to have slowly gotten " bright"

Again, I would recommend having your ears checked.  What you describe might be the start of hyperacusis, an ear condition.  

If it is an equipment issue, my bet is on the speakers.  But, it would be extremely unlikely that both speakers have the same degradation, and to the same degree, so listen to each one alone to determine if there are differences between the two.  If they sound the same, the problem is probably elsewhere.

Do you have a tube preamp?  Could the coupling caps be going bad?

Op’s ears became more natural sound mode from un-natural Hi-Fi ear mode. Many people (almost women, non-audiophiles) are always in natural sound mode and they hear un-natural Hi-Fi sounds as bright and noisy.

All Hi-Fi systems sound like a left speaker in below video. Alex/WTA

We can only guess without knowing the whole setup. Could this be an outside issue with your electrical, something introducing a lot of noise in your house or neighborhood?

Ironically, age related hearing loss can produce this. If we lose certain frequencies, others become more noticeable. So loss of highs can result in upper mids sounding prominent, especially in the sibilance range. Just another joy of aging.