Thank you for your question, Lindsay.  I am afraid that the photos are not taken from a close enough range for an identification of rust, a fungus needing a Sitka spruce tree nearby in order to complete its life cycle.  But, here is the PNW description of this disease and control recommendations:  http://pnwhandbooks.dev.extension.oregonstate.edu/plantdisease/host-disease/rhododendron-rusts
Note that only the fungicides marked with "H" are available for homeowners' use, and should be applied only in accordance with label directions.  
In all candor, it appears that the leaves are chlorotic, meaning they lack chlorophyll, which causes them to yellow due to inadequate nitrogen.  This may be caused by too little fertilizer, rather unlikely if they are from a nursery.  If you check on the undersides of the leaves and find black spots, they are likely infested with the azalea lace bug, described here:  http://pnwhandbooks.stage.extension.oregonstate.edu/insect/hort/landscape/hosts-pests-landscape-plants/azalea-rhododendron-azalea-rhododendron-lace-bug
I hope at least one of these is helpful.  Good luck!

Hi there, 

I believe the black spots are azalea lace bug frass.  I cannot identify the problem(s) on the leaf tops, and will need to refer you to Dr. Jay Pscheidt for help.  He may require you to submit samples.  I will send him an email and ask that he respond directly.  Sorry I could not help.

Thank you so much for taking a look! I look forward to hearing from Dr. Jay Pscheidt. 

I do see the leaves in the images and the discoloration that you are calling rust. This is not the fungal disease rust so you can stop thinking about that.
The leaves are chlorotic as Kris mentions and that is what catches my eye first. They look very much like they are deficient in nutrients. With Rhododendron that might easily be explained if the soil pH is too high. They really like a more acidic pH. We only see the last flush of leaves and the length is short also indicating a slower growth.
I see the brownish coloration or netting of the leaves that is prompting your question. These are also not any particular disease problem and may be part of the nutritional issue.
You could take a soil pH and see where it stands. Also, check to see if the plants are root-bound in those pots. These plants may do well in your garden if they have the right pH and good drainage and planted correctly. Good luck. 

Here is an OSU publication with a list of nearby testing labs:  https://catalog.extension.oregonstate.edu/em8677/html   Some will provide recommendations on soil amendments, if needed, but you have to ask, and tell them your plant species is rhododendrons.

A big thank you to the Master Gardner team and Jay! I’m so glad to know that it is not a fungus/disease that is occurring. I will be planting the Rhododendron’s in the ground soon and will use G&B’s acid planting mix to get the nutrients back up.