I sail Miracle 3078 with a plywood floor. The self bailers are Andersen Super Medium with six bolts. They have recently started to weep with relatively small amounts of water coming out from between the plywood and the top plate. I am guessing this is not unusual. Has any member experienced this before and what was the solution?

Do I just tighten the bolts or is there a bigger job to do?

I would suggest you really need to investigate first, remove bailer, dry woodwork and examine re varnish edges when dry refit plate with silicon sealant and around the bolt holes too
Good Luck
John