Just a few suggestions. Have a monthly meeting of the CNA staff. Address any issues. Get suggestions from the CNA staff on how to improve culture. Talk about what has to be done and is non-negotiable. (ie: up, dressed and to dining room by 8am, baths and showers by 11am that type of thing). Set up a shared governence team that really gets down to making patient care effective and the culture a workable one. The CNA staff can be their own advocates, their own voice.
Establish rotating "charge" CNA's. That would be a go to for any issues that may be brewing on a shift.
Have the CNA's work in teams of 2. Have one of the set be specific to stocking and other non-patient care activities and rotate the team, so the each week there will be at least one day of no patient care by that team. If you have enough CNA's one day a week a team could also be specific to bells and covering for breaks and lunches, again rotating.
Another idea is to have the "lead" CNA be the FBS, weekly vitals, making and maintaining the flow of teams on the floor, who's doing bells, and who is doing stocking, etc, and rounding to be sure people are doing what they need to be.
Make expectations clear at the begining of the shift.
Ask administration to have an LPN (or even the most senior CNA) be specific to supervising the CNA's, and establish a progessive form of discipline. Constant write ups go nowhere if a written plan is not put into place to change behavior, or if there's no consequences.
Be clear and thankful. CNA is a difficult and demanding job. Tempers flare when someone is overwhelmed, not supported, or feeling defensive that someone may think they do not know how to do their job.