The OP did not ask for opinions regarding his lifestyle change, just if he should tell his parents and how. No one picked up on the fact that they are undergoing other stresses as well.
I think perhaps the OP might like to discuss this with their Rav or someone they are close to. Medical issues and or age of the parent should be taken into account. Assuming this sudden news wouldn’t have severe adverse affects, I’d advise the OP to share it with them, perhaps in a letter initially.