What could be the issue with my water tank leaking from the back?

I notice yesterday that there floor surrounding my water tank was wet. When I turn on the faucet for cold water, the water would sometimes become hot and then go back to being cold. On the third picture, I circled parts of the tank and the floor that are wet (water doesn’t appear to be leaking from the bottom of the tank). On the third picture, the bolt for cold water is rusty, while the bolt for the hot water is perfectly okay.

Currently trying to get ahold of a plumber, but getting no luck. Would appreciate help in diagnosing this issue.