Welcome to XXXXXXX and thanks for your query.
A. Yeast infection needs treatment only when it is Present. Otherwise preventive methods are enough which are
1. Hygiene- clean the penis at showers with regular soap and water after retracting the foreskin.
2. Looking at factors that can suppress resistance like diabetes
and long term corticosteroid Intake.
B. Skin length- The penis and scrotum
are organs that can expand and shrink depending on temperature changes and sexual stimulation. It may just be normal. Ageing is not known to cause such changes. It is unlikely to be anything serious.
If worried, a consultation with a urologist
Wishing you good XXXXXXX