Sores / cuts on my 2 Plecos

I have 2 1foot plecos in a 55 gal with rocks and after I put in some frozen Squid I got from a pet store one of them (Chuck, the smaller one) started freaking out. He would flinch when ever he would lay on the sand and flip around the tank more than he would usually. Yesterday he flipped so hard that he actually came out of the tank. Now my larger Pleco (Norris) is starting to do the same thing and also flipped out of the tank about an hour ago. I have noticed red sores on both of the plecos. On the bottom of their tail fin and towards the back of their rectum. They also both have identical sores on the base of their dorsal fin. I put aquarium salt in today as I didn't have anymore and had to get some and also have been putting Meal-flex in the past two days. I tested the ammonia and it is reading "0". Please help me it would kill me to lose these fish. :barf::barf::barf::barf:

If i get any replys I will post pictures.

Thanks for the reply's, I'm new to aquariacentral and I thought that I would get an email if I got any replys to my post and was unaware of any of you replying to me. It turns out that both of the Pleco's had some sort of parasite that gave them seizures that in turn gave them the sores I was originally talking about. The plecos would freak out and swim full speed into the rock/coral thus giving the scrapes and sores. I got a parasite medication and Melafix. The effects were immediate, the seizing stopped in about 2 days. Then my larger pleco, Noris, started seizing again and died some time this morning.