SanDisk stock experienced a significant decline, with reports indicating a 14% drop in a day, although one outlet mentioned a 26% plunge. The decline appears to be part of a broader sell-off in semiconductor stocks, with other companies such as Intel, Nvidia, AMD, and Micron also experiencing losses. The reason for the decline is unclear, with possible factors including a potential threat from an in-house chip and the arrival of a new competitor, as well as uncertainty over whether the AI memory boom is losing momentum.