Could be a lack of vitamin C. Vitamin c is directly destroyed in the process of converting pro collagen to collagen. Collagen is the principle macromolecular protein in animal bodies ( humans including). Scurvy was manifested by systemic and widespread bleeding, and opening of all wounds because of the lack of vitamin c needed for collagen synthesis. Just because you do not have scurvy does not mean you do not have a sub clinical form of scurvy, hypoascorbemia that is being physically manifested by slow wound healing. Either way, taking more vitamin c will not only optimize wound healing, but also scavenge free radicals from oxidation, strengthen and support arterial integrity.
Recommended dosage.. Really doesnt matter but the RDA is vastly lower than what it should be. Given the fact that 99% of all animal species produce their own via in c in either liver or kidneys via biosynthesis from ingested glucose. The average amount produced daily calculated to a 70kg human being is 10 grams daily. It's completely safe, and non toxic. With up to 250 grams being used daily intravenously in cancer treatment.
Give it a shot, if it does not address the wound healing problem, it's effects will greatly optimize a wide variety of bio processes .