U.K.) how do I take this this?

I was working as a waiter on a quiet midweek day and I was taking finished plates back to the kitchen when I felt a stare and immediately looked to my right and 1 of these 3 girls was smiling/smirking at me and looked me down at my side/arm when I looked at her (im tall and lanky and my arms looked a little bit big too because I had a one or two layers in underneath) it was for about 3 seconds and then as I walked out of sight I heard a slight noise (couldn’t make it out) a bit later 2 of them were ordering food at the bar and on their way back I felt a stare while I was standing at the kitchen gantry bored and looked over to one of them girls (the friend of the girl who smiled at the start) on her own walking back to her table and when I looked over she laughed hard and put her hand to her mouth still looking at me then I looked away. I immediately got upset about if and I went to my team leader and assistant manager and refused to take their food to them regardless, I wanted them kicked out but my team leader wouldn't coz he said I can't be sure they were making fun of me, (I think they were) later on I had to check the toilets and I walked upstairs to girls toilets and the door opens and it was them girls I looked up and the girl that laughed earlier smiled at me, and I overheard em saying whys a boy going in girls toilets and walked past me as normal. but were they putting me down? I’m a guy btw

This is me if it helps:

https://m.imgur.com/a/YlAAhlA

(3 photos)