Need a photo really? In what way is it looking unhealthy as they are very pale leaved trees. Has it suffered recent damage? They are fast growers and can be brittle. It has the pairs of short thorns at the base of each leaf?is this what you mean?

It also leafs out quite late. You may want to give it a bit more time. I am watching my Gleditsia 'Sunburst' with trepidation at the moment as it also leafs out late.

There also seems to be problems with the cultivar 'Frisia' in recent years, and nobody knows exactly what the main causes are. main symptoms are either coming into leaf late, wilting of new foliage thereafter and branch die back. tests are ongoing at the RHS, and they advise anyone experiencing problems to send samples to them.