It’s rare that glans remain soft and rest of penis become harder. Need to take photo while in erect state. It’s might be your over expectations. And at age of 30 you are using tadalafil is surprising. Take proper consultation and counselling sessions otherwise how will you do sex in rest of your life without medication..try to keep these weapons for later half of life.

When you have normal erection, I don't think you have anything to worry about.