Adoped pit bull and dog on dog aggression

We adopted a female pit bull who is approximately 2 years old in August. She is such a pleasure and from the moment we got her, she has got along with our male Staffie and 3 year old female pit bull. Our dogs are walked/run twice a day in the nature reserve that borders our home. All dogs are allowed to walk and run off leash in the reserve so we encounter so many dogs each day. They are walked in the early morning with my husband and then with me in the late afternoon. As our two other dogs are very well socailized, we have never had any kind of dog aggression. Our new pit bull (Ice) has taken to snapping and launching herself at other dogs when we are on our walks, even tiny little dogs. She seems worse on leash, so we have now muzzled her on her walk and let her walk off-leash to try and let her have her space. On our first interaction she was really good and just growled as we went past 3 other dogs. Yesterday, she snapped at one dog, and then just walked past 2 others. Is there anyone who can help or give some advise if we are doing the right thing? It has only been 2 months and I know we need to be patient. Her aggression just really seems out of character as she is so goofy and loving at home.