See these lines in module_cmu_dvode_solver.F, which contains the subroutine dvode, the double precision ODE solver called from module_cmu_bulkaqchem.F
! in the output, istate has the following values and meanings.
! 1 means nothing was done, as tout was equal to t with
! istate = 1 in the input.
! 2 means the integration was performed successfully.
! -1 means an excessive amount of work (more than mxstep
! steps) was done on this call, before completing the
! requested task, but the integration was otherwise
! successful as far as t. (mxstep is an optional input
! and is normally 500.) to continue, the user may
! simply reset istate to a value .gt. 1 and call again.
! (the excess work step counter will be reset to 0.)
! in addition, the user may increase mxstep to avoid
! this error return. (see optional input below.)
It looks as though you should be ok, though it's possible these warnings would go away if you decreased the time step. I know yours is 6*DX, though it may just not be enough.