Shedding happens normally with the newly grafted hairs or shock loss can occur with you native hairs. Either way both are normal. I don’t think you have too much to worry about.
Thank you for your question. A second hair transplant is possible since you had 1500 grafts transplanted in the first surgery. To define the possibility of the second hair transplant, it will prefered to analyze the pictures of the donor area and the recipient area.