After a growth spurt featuring a hot stock price that at one point topped $100 a share, Barrett Business Services Inc. said Wednesday it’s experiencing “growing pains” and is making adjustments to put the company back on track.The Vancouver-based firm, a supplier of staffing and outsourced human resources services, reported a net loss of $3.6 million in the first quarter, or 50 cents per share. That compares with a net loss of $2.5 million, or 36 cents a share, during the same three-month period in 2013.First-quarter losses, however, aren’t unusual for Barrett. Historically, it incurs such losses because of higher payroll taxes at the beginning of each year.What was unusual — and what came as a disappointment to investors Wednesday, as the company’s shares were down by as much as 9 percent following Barrett’s first-quarter earnings release — was Barrett President and CEO Michael Elich’s comments about a wrinkle in how the company vets its clients. That process has traditionally driven a 90 percent-plus retention rate.However, Elich said, over the past several months the company has had to cancel its relationships with a number of clients who were using a “disproportionate level” of the company’s resources. Some analysts have suggested Elich’s statement means the company expects reduced revenue moving forward.