The joy of communal laundries. Have you referred to your by-laws, unless there is a bylaw in place regarding the use of these laundries then any notice the executive committee may place there is unenforceable.
Whilst it is impossible to answer your last question, it may be better for the owners corporation to consider the use of washing machines which incorporate heating coils internally than providing hot water from an external source.
Depending on the space you have available, have you considered buying your own dryer and installing it within your own unit? Then you wouldn’t be facing communal dryers contaminated with smelly and unhygienic substances.