Yellowing Arbor Vitae
Please send us photos of the trees so we can see what you may be dealing with. Send clear photos of the whole trees, around the base of the trees, and affected branches. Possibilities include poor planting techniques, excessive mulch, planting too deeply, poor drainage, etc.
It looks like your Arborvitaes are suffering from winter damage and also possibly poor establishment. This bronzing color can occur in evergreens as a result of winter temperature fluctuations and/or drought stress. It is also referred to as "winter color" on evergreens. Refer to our website for additional information. https://extension.umd.edu/hgic/plants/trees-shrubs/tree-and-shrub-problems/cultural-and-environmenta...
We also note some minor tip dieback. This could be a symptom indicating that the roots haven't established well. This can occur if the plants were root-bound in their pots and the root systems weren't spread out into the planting holes. Too much or too little water in the first year after planting can also lead to a failure of plants to "take." I suggest taking a "wait and see" approach. Keep the plants well-watered in dry periods and see if they push out new growth this spring. A light layer of mulch (no more than 2-3" around the base and not touching the trunks) can also help to retain moisture.