Home Improvement Questions? Ask a Handyman for Answers ASAP
This does sound like its the transformers at fault which take the 230v mains voltage and drop them to 24V for the bulbs to use.
Can you upload a picture of the transformer and also the lights fitted in the cupboard, so I can get a better understanding of the type of setup, as there may be a cheaper option to buy a larger transformer to power all the lights rather than replacing each transformer.
Lastly do you have access to a multi meter, in order to check if power is being output to the led's?