Pretty much everything everyone else said.
I am dealing with my aging voice and not sure how much longer I have. Had a couple respiratory things in the past year and in 2021, I stopped singing entirely for a year due to covid and my housing situation.
So I have taken breaks several times and I find it takes longer and requires much more care in selecting my exercise plan each time. I have a strange break in one spot, F (second octave) to be exact, that I can only catch when I have enough air to make it happen at mid volume. I have learned to work around it but it's there.
Never had any physical or health issues other than the regular ENT viral stuff but I have found that my posture is a culprit sometimes. There are days when I can't keep my lower back in line which reduces my air capacity and control and that's a thing because some styles of singing require some power, I can get the power but for only half the time I need. Like a reed instrument, if there isn't the properly controlled flow of air, the notes will not materialize.
I don't think I want to perform live any more as I am not confident I could pull off a full length performance anymore. It's been so long since I have that I really wonder.
I started getting therapeutic massages and they really help with the control and capacity problems.
I think you should take a hiatus from performance until you have resolved the issue, if you work out, only do it a couple times a week, only work your mid range until you feel like you can start stretching out in both directions, save working your high range for last. Stagger it in phases, work mid range then slowly add in the low range and eventually start locating your upper range. It matters that you do that.
Once upon a time I spent a decade of my life as a part time classical vocalist, other times other genres here and there. Do what you can to have a healthy diet and get good rest, relax your body and slowly rebuild to performance level.
Good luck.
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