They are getting medicated feed only have one brooder at the moment but going to see if I make a bigger one this weekend, also I have noticed one of them have been having diarrhea but haven’t noticed any blood in it
I would lean towards coccidiosis - it doesn't have to be all the chicks sick simultaneously for this to be the problem. If you start Corid today, you should see a big change by tomorrow. I would do this ASAP while the chick is still willing to eat and drink. When they're that small, it doesn't take that much to tip them over the edge.
Excellent article about coccidiosis with dosage information at the bottom for liquid or powder Corid:
http://www.the-chicken-chick.com/coccidiosis-what-backyard-chicken/
I would also be sure the chicks have somewhere far enough from the heat lamp to cool down. They really, really don't need the whole box to be 90-95 degrees- just an area to warm up. It would be like getting stuck on an airplane and the pilot can't turn on the air conditioning and you're not allowed to deplane.
For the first couple/three days chicks usually park it under momma hen. After that, they're out playing and they start coming back for quick warm ups under her.
If you can eliminate the heat lamp and use an alternative means of heat, like a Momma Heating Pad (aka MHP) - all you need is a heating pad that will stay on 24/7 to keep them warm. There's a monster thread with as many ways to make one as there are people who've done it.
It's also significantly less electricity used- much, much much lower fire danger- and your chicks will start sleeping all night in the dark - instead of becoming reliant on the light 24/7 and panicking about their first experience in the dark.
Here's the monster MHP thread if you'd like to eliminate the heat lamp:
https://www.backyardchickens.com/th...d-in-the-brooder-picture-heavy-update.956958/