If there is an issue, guests are more than entitled to ask for assistance. However, from what you have written, it sounds like your guests were unusually disgruntled, yet you were promt in addressing their concerns. I would begin the review by stating that they left the apartment clean and tidy upon departure, but emphasise that when a few issues that required clarification arose, your guests seemed disproportionately unhappy and disgruntled, and that the interactions left you feeling uncomfortable. You may also like to say that, once these matters were resolved, their comments began to extend to complaints about the apartment. You asked whether they would like to find alternative accommodation, and offered to issue a full refund, however they chose to stay. While you emphasised that they shouldn't hesitate to get back in touch if they needed anything, or if you could do anything to make their time at your apartment more comfortable, you didn't hear from them further, and hope that they had a pleasant stay.
If I read a review like this, I would assume that the guest was being unreasonably difficult, and if they have written something in their own review that is problematic, it shows that they both chose to stay and did not contact you again (which is particularly helpful if they say an issue was not resolved, was recurring, or if a new complaint is brought up).
