The “H” indicates that Clinton wrote the tweets herself. CNN reports:
Hillary Clinton told her Twitter followers she is “feeling fine and getting better” on Monday as she fights off pneumonia. The Democratic presidential nominee’s health was called into question after her early exit from Sunday’s 9/11 memorial service in New York City. Video taken at the scene showed her looking unsteady and requiring support to enter a van. The campaign said in a statement at the time that Clinton felt “overheated” and went to her daughter Chelsea’s Manhattan apartment to rest. Later that day, Clinton’s doctor said she was diagnosed with pneumonia on Friday and suffered from dehydration at the memorial service.