Read this thread on the main Les Mills International Forum.
Lots of recommendations were made there.
Ideally, you should only increase your weights by a small percentage. You should talk to your instructor before doing so.
In a side issue, with the constant mixing week-to-week increasing your weights should be done with a bit of self regulation. As you have no idea what the instructor taking the class is going to instruct that class. It would be wise if instructors made participants aware of the track selections in advance so that the participant can then make and informed decision to increase weights. Based on their previous history with the track, and what they were able to achieve when they last exercised to the track.
In reality, instructors should work with the same mix for a few sessions so that class members can make an informed decision to increase their weights. The rationale would be that motor pattern adaption can only really occur when an exercise is done repeatedly over a period of time. Learned motor pattern adaption to exercise. In reality, this cannot occur when a new motor patter is introduced. The end result would be redundancy of the previous motor pattern adaption learned. Adaption to a new motor pattern can only be learned if there is a repartition in the same exercise over a period of time. The end result would be a learned new motor pattern. In saying this of an instructor works with the same release over a period of time then (new motor patterns) can be learned and adapted to. Based on this the participant then can increase their weights based on a new motor pattern learned. They then can increase their weights based on a informed decision made.
The other contributing factor is that this a group exercise class and ideally the participant would talk to the instructor about increasing their weights.
The participant is just that they rely on the instructor to guide them through the exercises. It is your choice to increase your weights. If you need to do so please make sure you do this under guidance.
You need to do this in small percentages and only if you are 100% confident your ability to do so as this is a group exercise class not a personal training session.