How did the bottom get scratched? Were they used for other purposes? How deep and rough are the scratches? Good scrubbing and thorough sanitation should be able to get them sanitary enough for beer, unless...
The lids, the groove mainly, are bug traps. It's essential to clean everything that touches your chilled wort and beer thoroughly, followed by rinsing, then sanitizing (Starsan). Yes, the rubber grommet and hole in the lid are part of that system, as is the airlock.
Grain dust will settle on everything, but should not get inside your fermenters, until... you open them. To prevent that, before you open, clean underneath the lid rim by spraying or mopping with a washcloth soaked in Starsan. Then clean and sanitize before replacing. Mop the bucket rim too. I'm a strong proponent of mopping with Starsan, not just spraying.
Do you open the fermenters frequently, to take samples and so? There are better ways.
I still use plastic brew buckets from 2013. No problems, ever.
That said, those Fermonsters look like a very viable alternative, if treated right. That spigot needs some attention though.
I’m not sure how they got scratched as I only use them for homebrewing. Sometimes I use to aerate with a plastic mash paddle. But I stopped doing that. I bought 3 fermonsters and it’s 3 weeks in with no signs of infection so I think either the scratches or not sanitizing the lid was the problem.