[unkownfl]

If the belt is smooth on both surfaces then get a new tensioner spring. Compare before installing the spring. If the spring is ok then the belt stretched. Your spring or belt may have stretched. Smoke may have been the pulleys locking up from a bad bearing or a clump of grass getting caught when the mower was off it became dislodged from the topside of the underneath of the cutting deck. Grease those fittings with a grease gun until clean grease comes out of the spindles from the blade side or the pulley side. Grease each use of the mower because you got two acres and those are light duty spindles. I like moly grease and the gun from harbor freight should do the job.
If you got to mow grass before the parts are acquired you could remove the inside jam nut after removing the rod install some washers or spacer between the nylon lock nut and the threaded tensioner anchor. Check everything for clearance but it should give you some more tension on the belt. but thats rigging it and who knows about the geometry of everything.