Sick African Dwarf frog?

So I have no idea what's wrong with my frogs. I bought 3 on Sunday and they seemed fine Monday night right before I went to bed. I didn't feed them on Sunday because I read you shouldn't since they're stressed already. Monday I got called into work early and was gone most of the day, so, I know it was bad of me, but I just fed fish flakes and dried blood worms. It was really late though so I didn't really watch to see if anyone ate. I was gone all day Tuesday, like 8am-10pm but I didn't see anything out of the ordinary before I left, though I didn't have much time to really look. When I got home Tuesday, two frogs were not doing well. One was on his back on the bottom of the tank, but when I moved him with the net, he squirmed a bit but didn't try to get away. The other one was floating on the top, but he also didn't try to move away when I nudged him with the net. The 3rd one I could NOT find for the life of me. I took the other two out and put them in a smaller container with less water so they didn't have to struggle to get to the top for air and I noticed they both were trying to position themselves half out of the water. I put some thawed frozen blood worms in a little dish in with them hoping they might eat, but no luck. I went to bed and when I woke up, I saw the 3rd missing frog in the original tank, but it was dead. Must have died in the night. The other two managed to make it through the night, but one was still in really bad shape and the other seemed a little more active, but still not great. I went to Petco with the dead one and they tested my water and it was fine and couldn't think of why they were dying. They don't have any signs of diseases (no missing limbs or toes, no white patches, clear eyes, etc). The 5 gallon tank is heated, filtered, and only another female betta in the tank that doesn't really bother them. My 2nd one is now dead and I have one remaining. I bought her a nesting box thing to keep in the original tank because I figure it's better off with a regulated temp and filter. I also bought some stress coat and added it to the water. I didn't want to get any medications since I can't tell what's wrong. The last one is swimming around more than last night, but still not really dodging attempts to be caught by the net and hasn't eaten. I'm not sure if it's healthy swimming, or stressed swimming since this is the first ADF I've had (kinda floats, sometimes swims to the top and darts back down). Any ideas what I can do to help the remaining one? Before the 2nd died, he was kind of swimming around like he was drunk, if that helps any.