Memory and storage stocks are selling off sharply Monday morning as a weak second-quarter profit estimate for South Korea’s SK Hynix rattled the AI memory trade. Micron Technology (NASDAQ:MU<\/a>) stock, SanDisk (NASDAQ:SNDK<\/a>) shares, and Western Digital (NASDAQ:WDC<\/a>) stock were each down 6% a few minutes after the day’s session started. <\/p>\n The moves come after historic runs. Micron stock was up 243% year to date (YTD) through Friday’s close, SanDisk shares had climbed 707%, and Western Digital stock was higher by 238%. Today’s 5% pullback trims only a small slice of those gains. <\/p>\n Renewed U.S.-Iran headlines and the ongoing debate about the payoff on AI capital spending sit in the background of these stock declines. However, specific events surrounding SK Hynix are hitting memory\/storage stocks particularly hard. <\/p>\n Weak SK Hynix Estimate Triggers a Memory Reset <\/p>\n The trigger came from Seoul. South Korean brokerage KIS published a Q2 2026 profit estimate for SK Hynix 8% below consensus, citing slower-than-expected HBM4 (high-bandwidth memory) shipments and heavy reliance on HBM contracts. That call cut into the core bull thesis for the entire memory complex. <\/p>\n SK Hynix stock fell 15% in Asia, its largest single-day drop ever, a stunning reversal from its strong U.S. NASDAQ debut on Friday. Samsung slid alongside it and the KOSPI dropped 9%, triggering a 20-minute trading halt. U.S.-listed SK Hynix shares were set to open sharply lower after Friday’s debut. <\/p>\n July 16 is the Final Day to Tap Into the Lithium Boom (sponsor) Here’s why you should do the same before their July 16 investment deadline: lithium prices are up 75% this year, with demand projected to grow a staggering 5X by 2040. <\/p>\n With tech that can recover up to 3X more lithium than traditional methods, EnergyX is preparing to unlock up to 15M+ tons. Become a private-stage EnergyX investor before the July 16 deadline<\/a>. <\/p>\n Story Continues <\/p>\n U.S. memory names sold in sympathy. SK Hynix is Micron’s most direct competitor in DRAM and high-bandwidth memory, so any signal that HBM4 shipments are slipping raises questions about pricing power across the group. The reaction reads as profit-taking plus a scare that the memory super-cycle’s momentum may be cooling. <\/p>\n Peers and the Memory ETF Feel the Ripple <\/p>\n Seagate Technology (NASDAQ:STX<\/a>) stock is down 4% to $869 this morning after a YTD run of 231% through Friday’s close of $910.34. The hard-disk maker trades on similar AI storage tailwinds as Western Digital, and both are moving in tandem with the DRAM and NAND names. Seagate stock also carries a beta of 2.07, so its swings have tended to run larger than the broader tape in both directions. <\/p>\n The Roundhill Memory ETF (NYSEARCA:DRAM<\/a>) is taking a bigger hit than the U.S. constituents, with the ETF down 9% to $57.52. That reflects concentration: the top three holdings, Samsung Electronics, SK Hynix, and Micron, account for 73% of net assets, and the Korean names are leading the losses. The ETF is a narrow, non-leveraged thematic fund, and today’s move highlights its single-region concentration risk. <\/p>\n Sell-side conviction hasn’t evaporated, though. Citi recently reaffirmed a Buy on Western Digital with an $800 target, well above Friday’s close. That constructive analyst view is being overshadowed by sector-wide selling this morning. <\/p>\n What to Watch Now <\/p>\n The bull case for Micron rests on durable AI-driven memory demand. Micron’s recent Q3 FY2026 results showed revenue of $41.5 billion, up 346% year over year (YoY), with non-GAAP EPS of $25.11 and gross margin expanding to 85%. CEO Sanjay Mehrotra guided Q4 FY2026 revenue to $50 billion, plus or minus $1 billion, citing multi-year Strategic Customer Agreements and HBM4 already in high-volume shipments. The bear case is memory cyclicality, the HBM4 shipment and pricing concern flagged for SK Hynix, and rich valuations after a massive run. Investors should consider keeping their position sizes modest given the volatility. <\/p>\n SanDisk’s own Q3 FY2026 report was similarly outsized. Revenue jumped 251% YoY to $5.9 billion, non-GAAP EPS came in at $23.41, and management guided Q4 revenue between $7.75 billion and $8.25 billion. The company also cleared $650 million in debt to reach a zero-debt balance sheet, giving it flexibility to weather any near-term memory pricing wobble. <\/p>\n Prediction market participants are leaning cautious near term. Polymarket odds place the highest conviction on Micron trading in the $930 to $960 range this week, with a 0.865 probability that shares finish today lower. Upside conviction above $1,020 drops sharply. <\/p>\n Still, Reddit sentiment tells a more bullish story. Aggregate sentiment on Micron scored 66 (bullish) as of Monday morning, and SanDisk sentiment on WallStreetBets held between 58 and 75 through the initial selloff, indicating retail dip-buyers stayed engaged. Traders can watch for whether the $920 level holds on Micron stock and whether the DRAM ETF stabilizes once U.S.-listed SK Hynix shares find a level after their delayed open, and could look for any updated commentary from Korean analysts later this week. <\/p>\n Meet America’s Newest $1b Unicorn (Sponsor) <\/p>\n A US startup just passed a $1 billion private valuation, joining billion-dollar private companies like OpenAI and ByteDance. 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