Small stocks underperformed the rest of the market on Thursday for the second straight session, and helping things along was Smith Micro Software's ( SMSI) plunge. Jeffries cut the maker of wireless-communications software to hold from buy, sending shares down $3.02, or 15.3%, to $16.71.

Boots & Coots International Well Control ( WEL), a Houston-based company that sells services to the oil and gas industry, offered 26 million shares at $2.10 apiece before underwriting discounts and commissions, half of which are being sold by the company itself. There's a 3.9-million-share underwriter's option in case of overallotment. Shares were losing 30 cents, or 12%, to $2.21.

Maryland's TVI ( TVIN), which makes shelter systems and other products, plummeted 21.6% to $1.09 after saying Chief Executive Richard Priddy and Executive VP Charles Sample had both resigned from the company. Wireless-equipment maker KVH Industries ( KVHI) slid 9.1% to $8.67 after breaking even in the first quarter. Analysts polled by Thomson Financial were looking for a profit of 4 cents a share; a year ago, the Middletown, R.I., company made 8 cents a share.

On the upside, North Carolina's PokerTek ( PTEK) surged 18.8% to $12 on word it will exclusively provide casino operator Harrah's Entertainment ( HET) with "live, player-banked, automated poker tables," pursuant to a "multi-year" deal. Harrah's recently lost 6 cents to $85.41.

Security-technology developer MDI ( MDII), based in San Antonio, Texas, announced that the city's ABC news affiliate featured the company in a special on school security. Shares added 13.8% to $2.15 in recent trading. Meanwhile, I-Flow ( IFLO) jumped after two of its products -- ON-Q PainBuster and ON-Q SilverSoaker Antimicrobial Catheter -- yielded positive preliminary results in a trial evaluating the effects of the devices on surgical-site infections. Shares were trading up 13.2% to $16.50.

Connecticut-based Playtex ( PYX) was 10.4% higher at $14.94 after the feminine-products maker bought out Hawaiian Tropic. Ivanhoe Energy ( IVAN) shot up 7.8% to $2.50 on word it will use its heavy-oil upgrading technology in order to jointly develop an Iraqi field with Inpex, if indeed the field is suitable.

And California's Exponent ( EXPO), which sells engineering consulting services, earned 31 cents a share in the first quarter -- a dime higher year over year and 8 cents past the sole analyst's estimate. Shares were leaping $1.81, or 8.8%, to $22.49.

The Russell 2000 Index gave up 0.5% to 820.32; the S&P SmallCap Index was off 0.3% at 422.06.

More from Investing

Market Can't Handle the Wild Ride: Cramer's 'Mad Money' Recap (Thursday 5/24/18)

Market Can't Handle the Wild Ride: Cramer's 'Mad Money' Recap (Thursday 5/24/18)

Musk's Tweets About Unions Draw Fire From United Auto Workers

Musk's Tweets About Unions Draw Fire From United Auto Workers

Replay: Jim Cramer on North Korea, Oil Prices, Apple and Carnival Corporation

Replay: Jim Cramer on North Korea, Oil Prices, Apple and Carnival Corporation

Gap Drops After Hours on Disappointing Earnings, Weak Same-Store Sales

Gap Drops After Hours on Disappointing Earnings, Weak Same-Store Sales

Canopy Growth: First Cannabis Firm on the NYSE Fails to Generate Buzz

Canopy Growth: First Cannabis Firm on the NYSE Fails to Generate Buzz