Martina McBride and group Heart are the latest to drop out after Barenaked Ladies and Willie Nelson canceled appearances at the Orlando SeaWorld festival.
Heart on Saturday became the third act and Martina McBride the fourth to bow out of the festival amid online pressure prompted by the documentary "Blackfish," which is critical of the park's treatment of killer whales.
Country singer Willie Nelson canceled Thursday.
Barenaked Ladies announced last week that it had decided against appearing due to the "Blackfish" controversy.
Other acts scheduled to come to the 2014 edition of SeaWorld Orlando's Bands, Brew & BBQ Festival set to begin Feb. 1 include Justin Moore, Scotty McCreery, Cheap Trick, REO Speedwagon and 38 Special.