Why has my cactus has turned red/ beige at its base?

Question

One of my cactus turned red at its base about a year ago and it has since spread upwards. Some websites say it is a natural ageing process but I doubt so because it is still so small! Now another of my bigger cactus has turned red at its base! Please advise.

First picture attached refers to my first cactus that turned red. Second one is the one that I just noticed turning red. The third one has got a band of beige at its base. When I try to scrape it, nothing happens.

The red parts are very hard, just as turgid as the green parts. I did not notice any rotting at the base. All my cacti feel turgid still, including the base.

[Second cactus that turned red

Answer 1

The first two pictures, where the base is red, do not look healthy at all to me. I doubt this is natural aging. It could be overwatering. The second one looks to me as if it is collapsing from within, so I would say it will soon be dead if it isn't already.

The third with beige on the bottom is likely just natural aging. Older cacti will often form a sort of "barky" or "corky" areas on their bottom stems. This one I believe is fine.