my one year old female cat mochi has suddenly lost a chunk of hair by the base of her tail. about a week ago, she had a small scab/bump which has now gone but she’s lost a pretty large chunk of hair. it’s literally like someone has shaved her. her skin underneath seems fine now. i first thought it could be from her playfighting with her brother but the hair loss has only gotten worse. i’m not sure whether to panic and take her to the vet or if it’s something to let sort itself out? please advise! thank you :)