Shoulders are wildly complex. A good physical therapist (in sports rehabilitation specifically) can give you some static and band exercises and stretches that’ll strengthen the weak points. There are 7 insertions in your shoulder muscle, and I think 7 in the chest, plus lats and shot all pulling willy-nilly on your shoulders, pulling them this way & that. When you start to grow, they change position a lot. Of course, most of us aren’t in a position to hire a sports physical rehab guy (or gal)….
I think Press is right, supplements are you best bet. Type 2 collagen, maybe MSM/chondroitin, fish oil

The shoulders as a whole are an extremely complex area made up of various muscles, tendons and joints. Its an area that if you like to lift heavy can take a real beating over the years as I have found myself. Rep ranges that you choose to work in a have a huge impact on how sore they get and keeping them in good general health. Sticking in the 6 to 8 rep range in benching and shoulder work is your best bet to keep them healthy and free from pain, once you start hitting the 4's and below you will find things like tendonitis can creep in, rotator cuff tears and joint tears can become a possibility. In terms of natural food options to help things I think you will be hard pushed to match the effectiveness of proper joint supplements - they are simply more effective along with various rotator cuff strengthening exercises and routines. You ideally want to be consuming supplements that strengthen the tendons such as Collagen Peptides, Vitamin C, Glucosamine, Chondroitin, Cod Liver Oil and so on.

You may find this useful too:

https://www.eroids.com/forums/general/over-40-trt/tendons-and-aging

Also, keep chugging that Glutamine as its a brilliant supplement to take - it helps with many functions including the digestive system and helping rejuvenate the gut lining etc.