Possible racism by KLM towards my parents?

Hello everyone, my parents recently flew with KLM from India to Toronto via AMS and I got to know that the crew were awful towards my parents especially from AMS to Toronto. My parents are diabetic and my mom have to take some medicines periodically. So my dad asked them a water bottle because it was a long flight and they did not hassle the crew for water. The crew? They did not bother to respond to my parents for 2 hours!. Then the crew went ahead lying to my parents that they ran out of water but proceeds to give to people in front of them? My dad says the people sitting in the front row were white and the crew happily served them beer 4 times in those 2 hours, but could not even server water to my parents. They had to wait until the last meal service to get their water. My parents waited for water. Oh the final straw was that they airhostess scolded my mom trying to use the washroom thats on the front in the economy class! WTAF Economy has 4 washrooms, 2 of them were not occupied and when my mom tried to access one the hostess was extremely rude and forced my mom to use the washrooms at the back, their were close to washroom on the front. They have been flying globablly for at least 10 years now this is the worst treatment, and honestly I am not sure what i can do. Should i file a complaint? would it be of any use? should i tag them on twitter or something?