@AlinFlorida Al I’d certainly agree with JK and use Justin’s Finger Stretching Exercise, especially Ex 3 and 4. I do general 4 fret chromatic runs E to e to E from 7th to 1st fret but also on each string horizontally but that is more about coordination than stretching. Ex3 and 4 really open up the finger span and I use this to increase flexibility.
Another no-guitar exercise is to put your left and right hand finger tips together, fingers apart, I guess like an open prayer position, And then press the hands together keeping both forearms in line at chest height. Again this opens up the span and can be done anywhere anytime. You can gently pulse to start then press and hold, the more pressure the wider the span but start slowly.
