There is one extraordinary minister of holy Communion I know who holds up the host and uses it to make a cross in the air before placing it in the communicant’s hand. Is this allowed?
Absolutely not. What this EMHC is essentially doing is giving benediction with the Eucharist, a liturgical action that is reserved to a priest or deacon. The document Holy Communion and Worship of the Eucharist Outside of Mass (.pdf file) states:
The ordinary minister for exposition of the Eucharist is a priest or deacon. At the end of the period of adoration, before the reposition, he blesses the congregation with the [Blessed] Sacrament.
In the absence of a priest or deacon or if they are lawfully impeded, an acolyte, another special minister of Communion, or another person appointed by the local ordinary may publicly expose and later repose the Eucharist for the adoration of the faithful.
Such ministers may open the tabernacle and also, as required, place the ciborium on the altar or place the host in the monstrance. At the end of the period of adoration, they replace the Blessed Sacrament in the tabernacle. *It is not lawful, however, for them to give the blessing with the Sacrament *(HCWE 91, emphasis added).
I recommend taking a copy of this document to your pastor, explaining to him your observation that one of the EMHCs is giving eucharistic benediction, and politely requesting that he take action to stop it.