Washington Homes Inc., a home builder based in Waldorf, Md., and one of Washington's 100 biggest companies, yesterday reported a more than 50 percent drop in net income for the fourth quarter ended July 31.

The company reported net income of $302,850 (17 cents per share), less than half the $641,472 (36 cents) for the like quarter a year ago. Revenue for the quarter was $19.2 million, up from $15.8 million for the year-earlier period. Net income for the year was $2.3 million ($1.29), slightly less than the $2.4 million ($1.34) reported a year ago. Revenue for the year was $61.5 million, from $54.2 million in 1984.

The company attributed the dip in fourth-quarter earnings to an extraordinary item associated with the Maryland savings and loan crisis that began in May.

Bay State Savings and Loan Association, of which Washington Homes owns 84 percent, was required to obtain federal insurance, the company said.

During the approval process, it became apparent that certain funds deposited by the company with the Maryland Savings Share Insurance Corp. might not be recoverable. In reaction, Bay State took a one-time extraordinary charge to earnings during the fourth quarter of $668,000.

*Schwartz Brothers Inc., a large record and video tape distributor based in Lanham, said its net income more than doubled in the second quarter ended July 31, to $179,872 (22 cents per share) from $84,505 (10 cents) for the like period last year. The company also said revenue increased to $15.4 million from $9.3 million for the comparable period. Officials attributed the gain to a surge in distribution sales of videocassettes.