Toilets, Sinks, Showers, Tubs and Disposals - Scratches appearing in toilet bowl

A couple of weeks ago, what I thought to be a hair in the toilet bowl turned out to be a scratch. Not too long after that another one appeared on the other side, both being under the water level. Over this past weekend we was away for 3 days and when we returned I noticed that these scratches were blackened (mold) and there was a new one in a different location and also in the very bottom where the water goes down there appeared to be a round one that looked more like a pitting than a scratch. I have been told that there may be something wrong with the toilet and it should be replaced imediately so that it does not break apart. I was just wondering what someone else might think and get more feedback. By the way my other toilets are not doing this so I cannot see it being the brush (that appears in good shape) or the cleansers.

Also, I should mention that the scratches appear to be getting longer.

I agree that the problem is a serious one. I would advise replacing it. Your statement that the scratches are getting longer, tells me that they are most likely cracks and not scratches. Good luck.