You asked a similar question about the tires/wheels on your 2017 trailer in another thread:
https://www.keystoneforums.com/forum...862#post364862
First, check the Keystone decal on the front roadside corner of your trailer for "OEM tire requirements"... If that decal (printed by VIN) states the tire size is 14", then that's what I'd use. When doing that, based on the three different brand tires that were on it when you bought it, I'd carefully inspect the wheels BEFORE installing new tires. If you're not able to inspect them, then bring the facts to the attention of the tire installer and have them inspect the wheels for you. Chances are, if you don't say anything, they'll just do a "quick cleaning of the rim, lube it and throw the new tires on the rims. They wouldn't suspect any problems unless you tell them the situation....
Going to 15" wheels/tires on a trailer with adequate load reserves is not necessary. Upgrading from 14" LRC to LRD tires will give you a good "safety cushion" on tire capacity.