Morning Botty,
Did you not neutralise the floor after using the stripper?
If your client has cleaned the floor using bleach on a regular basis, as stated before the damage has already been done, the floor will never look right again.
This situation is not your fault, improper maintenance, cannot be undone by using some sort of magic chemical. If they have not used bleach since the second clean, ask what they used, even better, ask to see the chem, as explained this should be a floor maintainer or nuetral cleaning agent.
If they are not happy with the floor, I would suggest that you offer to try to fix it one more time, but do charge them for this, strip the floor again, nuetralise the floor after the stripping process, rinse the floor 2 or 3 times, then apply the finish, and buff to a shine using maintainer and a high speed buffer.
Explain to the client, the floor must be maintained using floor maintainer, and spray buffed on a regular basis in order to maintain the appearance, unless the floor will revert to its present state.
As for which chems to use in future, any recognised make will work, the trick is to keep your eyes open, and ask any prospective client questions regarding their current cleaning programme, floors in order to look good, and remain safe, need to be properly maintained, if the client insists on ignoring this fact, you, the independent contractor should not be held responsible, we are cleaners, not miracle workers!
Regards,
Rob