I recently bought some new chairs for the kitchen but because they left indentations in the flooring I capped each foot with a black walking stick ferrule. BIG MISTAKE in only two days yellow marks have covered the floor where each ferrule rested. I have tried bleach, kitchen cleaner and white spirit but to no avail. I have replaced the ferrule with pieces of stick on felt which I did not realise were available. Can anyone help as I fear I may have ruined the flooring. Thank you.