1987 Mazda RX7 complete loss of power I NEED HELP!

Engine Performance problem
1987 Mazda RX7 Two Wheel Drive Manual 70k miles

a lil over a year ago I had purchased an 87 rx7 turbo 2. Im the 3rd owner and know the 2nd and have talked to the original. This car is absolutly immaculate! On the down side of that it has sat either in a garage by the first owner or outside and only drove literally 2 miles a day. I started driving it and after about 600 miles it is a dust magnet in my garage. As soon as I started driving it it slowly staarted losing power more and more every day. So I take it to a forien auto specialist and aske him to do a vacuum test and he must have not heard me and he does a copression test. So his results return 5 good chambers and the last dropped compression. Now im no mechanic but I have helped my dad tear motors down and rebuild my whole life, anyway, I know how rotorys work. Now the mechanic tells me its an apex seal. But if it was an apex seal, wouldnt 2 chambers have lost compression? Again im an electrician by trade and I figured that out in my little head. Anyway the drop in pressure on that last chamber was the comression stroke since theres no valves right? Anyway needless to say im still stumped with whats goin on. I NEED SUGGESTIONS AND RTORY EXPERIENCE! Thank you greatly for listening to me ramble!