You should always start with something positive. Always document your conversations.,
Only have one documented coach per week to give them time to improve. However if you are coaching for multiple different problems, like one for productivity , one for attendance, one for long breaks, those are all different so you can document all of those separately in the week if that makes sense.
Always seek to understand if there are other issues effecting their performance first. Offer your assistance or direct them to HR if they feel the need to utilize the many benefits spot offers.
Try and get the point of how there performance effects the rest of the store.