Certified GKH Gardening Expert
It is possible, but it is even more likely that the soil is either infected, or lacks phosphorus and potassium. Adding these two will (or a simple bloom booster at 1/4 strength) correct acidic soil, as well.
In the case of infection (This treatment should be a part of your yearly care anyway) you can use a handful of DOLOMITIC LIME and a few tablespoons per shrub of WETTABLE SULFUR. This will help kill off infection, as well as provide some relief of a few common deficiencies, such as: Sulfur, Oxygen, Carbon, Calcium, and Magnesium.
This article will give you more information on the care of these shrubs: https://www.gardeningknowhow.com/ornamental/shrubs/firethorn/care-of-firethorn-bush.htm