How much Epsom salt you been using? Sorry Blue is your betta am i right ? I know you have other fish so i want to make sure it betta because not every fish tolerant to the salt. While you don't have any medications i would really add 3tsp/gall of the Epsom . Do not afraid to stress him with Epsom it very mild and not going to harm him or stress him out. So add 3tsp/gall and do daily water changes (100%).
Pineconing is a symptoms which can be due to many reasons. One of the reason is internal parasites. Is he bloated? Did you see his poop? Is it normal color or it white,clear, broken white stringy ,wormy shape?
Do you have an idea which medications you need to look for ?