They are not huddling. They are fleeing to the extreme outskirts but can't flee the confines of a too small brooder so they crowd, risking trampling and smothering.
If 30C (86F) is the temperature of the entire brooder, these chicks are in danger of not being able to shed excess heat, and they will experience heat stress and die very quickly from it.
You are already observing your chicks' needs. So ignore those stupid heat guidelines all together and let you chicks tell you how warm and cool they need it to be. If the room is warm where your brooder is, 30C (80-85F) may be the highest the heat zone needs to be.
If your house or wherever you have these chick is very warm, you will only need a very, very small wattage heat source for the chicks to warm under. If the room is 30C (86F), you won't need any heat at all for the brooder during the day, and a minimal heat source at night.
With that many chicks, it's critical to have a brooder large enough that the chicks have a choice of very cool space in which to cool off, and one heat zone to warm up. They are a lot like lizards at this age, moving in and out of the warm zone to regulate body temperature. They aren't cakes baking in an oven that has to be kept a uniform temperature.
