BMO Capital analyst David Maris says investors are wondering why ZS Pharma (ZSPH) is down 18.5% over the past five days. The weakness, Maris argues, is largely attributable to risk-averse investors taking profits in a "weak tape" as well as peer company Relypsa (RLYP). The market seemed unhappy about the size and partnerships that Relypsa announced earlier this week, Maris writes in a note to investors. He keeps an Outperform rating on ZS Pharma and still believes the stock is worth $70. ZS management does not see any read-through from the Relypsa deals and its own situation, the analyst points out after speaking to the company. The biopharmaceutical company focused on treatments for renal, cardiovascular, liver and metabolic diseases is up 59c to $52.09 in early trading.