If you are filing a 2018 return (1041) for the trust and there was a net capital loss, then that net loss should be carried over to 2019; a nongrantor trust does not pass losses through to beneficiaries until termination and the trust files a final return.
You can mail the returns for both years but you should mail each separately.
I would still advise you to consult legal counsel and seek professional tax guidance.
