Most specialized credit card companies posted solid first-quarter earnings despite the tremors caused last month when Advanta Corp. preannounced a $20 million loss. Capital One Financial Corp., Dean Witter, Discover & Co., and MBNA Corp. attained double-digit earnings growth over the first quarter of 1996, while rising star Metris Cos. doubled net income. Earnings of other card companies will be trickling in over the next two weeks. Providian Bancorp and First USA are expected to report this week, while American Express Co. is to report next week. Rising chargeoff rates continue to trouble some analysts. They continued an across-the-board climb. "This looks like the worst quarterly increase," said Gary Gordon, an analyst with PaineWebber. "I've been concerned about it for two years."