Trailer Brake Fire

Not sure where to to post this one, I have a comment a thank you and a question all rolled into one here. so i figure here at least info will be seen and maybe new drivers can learn from my mishap.

Couple weeks ago was coming out off of a 10 hr break in western PA on I80 round 3ish CST. Had just come from Western OH enroute to MA. With absolutely no problems from OH to PA. I did, what I thought was a thorough PTI same thing I do every day regardless of weather or conditions. I grab my flashlight gloves and paper towel toss my flashers and lights on I hop out the cab and release the drivers side hood lock. I inspect the drive tires between em and behind em look for anything 'out of whack' check the air lines, give the drive train a once over and move on down. (I dont get my gauge out every day but do kick em make sure they still have air daily, gauge em maybe every week or two(never been the best with that)) Work my way back and check the trailer hubs probably more diligently than the tractor ones because Its always a different trailer and anything can happen so I LOOK for anything that seems wrong. again between behind, loose hanging anything that may seem 'out of whack'. Check the lights and seal on the back and do the same thing on the other side. By the time I get to the cab I flip the other lock check fluids and again 'anything out of whack' belts hoses whatever.
Nothing seemed wrong so I rolled. It was cold as explative out and there was a sheet of ice that I witnessed bulk hauler having issues with as i was getting coffee so i sauntered out of the parking lot. with no noticeable problem. The on ramp was close and It went right up a hill (pilot in Sandy Twp) and I was loaded fairley heavy 42K so didnt think much on the fact I wasnt gaining speed. Once i crested it got right up to speed (max 63) and no issues. then hit one maybe two mediocre hills but didnt loose any speed beyond expected dropped to mybe 58-55. Then I hit another large hill. Bout halfway up i realised I had an issue but i thought it was an engine issue. not enough power. at no point did i feel 'I was being held back' vs. not enough power. By the time I was cresting this hill I had a truck pass me and blow his air horn ( at speed as he kept going(I had my flashers on was at about 35- 40 mph)) Then a jeep something or other flagged me down yelling my trailer was on fire a couple seconds later. When i heard Her I, well let me move back. When the truck blew his airhorn I thought maybe he was just pissed i was heavy and moving slow, BUT i did look all around to see if i had an issue I didnt notice. I had my CB on and noone tried to contact me and I saw nothing but normal out my mirrors. So shes yellin sayin my trailers on fire, I dont see this but have to take her word so I pull off and, well sure as sunshine yup, all four trailer brakedrums are blazin.
Now my thank you goes out to the couple in the Jeep. Between calling 911, putting out the fire and trying to secure the scene, I never got a chance to thank you and when things were calm enough you had already mosied on down the road.
My comment goes out to the trucker. Im sorry. i missed the day in class or life where an airhorn blast at 70 at the top of a hill meant my trailer was on fire. maybe slow down and get my attention? or shout into the idiotbox which I had on mainly for any situations like that mine or others?
My question comes in with did I do a strong enough PTI? Did I miss something?(obviously i did) Should I have assummed brake drag when It felt like engine issues?I dont know. No one was hurt. No damage to freight. after repairs it was only like 6 bills including all 4 rear drums and shoe.