WASHINGTON – Senators searched for a balance Tuesday between increasingly lenient state and federal laws concerning marijuana. “Experts fear they will create a big marijuana industry, including a Starbucks of marijuana,” Sen. Charles E. Grassley, R-Iowa, said. Members of the Senate Judiciary Committee spoke at a hearing with people on the frontlines of the marijuana issue. Twenty states and the District of Columbia have laws allowing medical marijuana, and 16 of those have decriminalized possession of small amounts. Colorado and Washington have legalized the recreational use of marijuana.