Macron browning fast but underbaked at 300F

I'm using Pies Tacos recipe and trying to troubleshoot my macaron process. Currently one of my batches I baked a batch at 150⁰C (300F) for 13:30 minutes in the lower middle part of the oven. This one was the last batch which was runnier than the rest due to me not being great with a piping bag.

But, my question in this post is, why are the tops of my macarons browning so fast while the inside is still underbaked?

I see others here baking at 300-325F for 15-20 minutes and having crisp colors while mine are fully brown if I let them go for even 15 minutes. My oven temperature doesn't usually seem to be higher than the setting, it's usually spot on after pre-heating but the temperature seems to be even lower than intended during baking due to opening the oven and the thermometer more often than not shows a temperature below my set temperature (see picture 3). And yet, my macarons brown quickly.