Not sure what the weight is on your unit, but upgrading to at least D range is probably a good idea. Sure can't hurt. On the GY, I am assuming that you may have Marathons on your trailer. I personally have had very bad experience with Marathons, and would not use them again. Had two that sidewall separated and blew out while sitting in my driveway over last winter. You will find numerous other posts on the JOF that also reflect bad experiences with Marathons. Replaced them with Maxxis, and have had no further trouble.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.