Mmm... (more of a 'hmm' than an 'mmm good')
Can you afford to get new buckets?
Some would say "bleach kills everything" (in proper concentrations). And "you should be good to go" with proper soaking, cleaning, and rinnnnnnnnnnsing time. Potential problem I see is that if you are scrubbing hard to really clean everything, you could be leeching the chlorine into the plastic, and exposing this to your beer, creating chlorophenols and phenolic off-flavours.
If it was your first use, it is a shame to get rid of stuff but I'd say to be completely worry-free, get new buckets. But...yes...that's double the cost.
So the other hand says to let them soak for a few days, and use a proper cleaning solution and a rag (something soft) and rinse the HECK out of the buckets and try an inexpensive beer kit (a lighter beer, something that will definitely show off flavours if there are any). If you would rather spend money on the kit and your time involved.
So my advice is weigh out the options in time and money. You may feel better off with new equipment or you may wish to go through with the cleaning.
If it were me personally? I'd soak those suckers, clean 'em, use soft cleaning cloth, rinse the snot out of them, and give 'er! And if it turns out bad, it COULD be from the buckets, or any other step in your chain.
p.s. keep in mind that a lot of people swear by 'just using bleach' but to me: bleach/chlorine is a sanitizer (one that needs to be rinsed rinsed rinsed rinsed rinsed), not a cleaner. I guess I'm a believer in the nice soapy suds when cleaning and like to use no-rinse sanitizers, myself.