Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Stocks finished mixed on Tuesday, with broad-market indexes like the S&P 500 and Nasdaq Composite posting solid gains even as the well-known Dow lost ground. Yet even while many stocks rose, today was a bad day for Amarin (NASDAQ:AMRN), Walter Energy (OTC:WLTGQ), and Skechers USA (NYSE:SKX), all of which lost substantial ground on the first day back after the Martin Luther King, Jr. holiday.

Amarin plunged 24% after the biopharmaceutical company said that the FDA had denied its request to reinstate its special protocol assessment for its Vascepa drug. Amarin had hoped to expand the drug's use to make it available to patients with less severe levels of high-triglyceride counts, but the Division of Metabolism and Endocrinology Products weighed in against the request. The move forces Amarin to undergo a much longer process to try to obtain the more lucrative indication, given how many more potential patients fall into the less extreme cholesterol-count category.

Walter Energy declined 8% on a bad day for coal stocks generally. Metallurgical coal rival Cliffs Natural Resources (NYSE:CLF) dropped 5% after analysts at Goldman Sachs predicted that copper and iron-ore prices would fall dramatically in the coming years, and even though Walter Energy doesn't have iron-ore exposure, the general picture for metallurgical coal demand could face the same challenges if steel prices stay low. Combined with poor prospects for thermal coal, Walter could face continued difficulties barring a surprise in industrial activity globally.

Skechers USA dropped 7% after analysts at BB&T Capital Markets downgraded the stock. Yet the footwear-maker got some support from other analysts, as both Sterne Agee and Susquehanna defended the company's business. Susquehanna in particular noted that its indications show that sales and margins appear to be consistent with its expectations, yet those positive views weren't enough to overcome the negative sentiment. Given the troubles that many retailers have had following the holiday season, Skechers' performance today isn't all that unusual.