Calculating (or not calculating) lost earnings on late discretionary c

[MR]

We have a new client that transmitted 401(k) contributions late in 1998 and 1999. We are currently calculating a rate of return on those contributions so that they can deposit the lost earnings to the plan. They also had a 1997 discretionary profit sharing contribution that was not deposited until April 1999. If they did not take the deduction for that contribution for 1997 and were well within the 404 limitation, should they deposit "lost" earnings on the discretionary contribution? My first thought is no, since this is a discretionary contribution, unlike the failure to transmit 401(k) contributions on time.