It looks as if it dried out a time or two. Not seriously, but keep it damp.

@akamainegrower I have them planted in the container in fir bark, so it is moist but fast draining soil. I water about three times a week.

So it is frustrating to me when the same symptom can be caused by either not enough - or too much - water. How do I figure out which?

It is frustrating and sometimes impossible to figure out precisely. The explanation for the browning is usually that the plants withdraw moisture from the leaf extremities first - tip or edges. This happens very often when there's too little water. Too much water can damage roots which then triggers the same response. Likewise with soaking then drying out excessively when it happens over and over again. Excessive fertilizer salts are not flushed out from the container mix can be another factor. Air temperature and the temperature of the planting medium are also involved. Your planting medium should be fine. The goal, however difficult it may be to reach, is consistent moisture with no extremes. Thinking in terms of weather, temperature, frequent checking of moisture content with your hands can help. A specific number of waterings a week is not likely to meet the plant's need every week of the year.

@akamainegrower would there be any value in completely removing the plant from the soil and seeing how wet it is at the bottom of the container?

Now that it is approaching winter, with the night time temperatures below 50F, how many times a week should a rhododendron get watered?

Sliding the plant out of the pot - without totally removing it from the soil - enough to check the bottom of the pot might possibly have some value. You could also check for root damage. This would indicate excessive moisture. Also make sure that the pot itself has adequate drainage and that the container is not too large for the root ball.

It just isn't possible to say how many times a week to water given all the variables involved. A container with good drainage plus a coarse, free-draining planting medium (which you have),and I would think one good soaking per week would be enough, but you have to go by what you observe.

It may also have just been up potted and has a small, unteased rootball hiding in the current pot and doesn't have enough root surface yet to effectively absorb enough water to completely hydrate the leaves. Probably not in this case, but it is another variable to consider. I always check the rootball before purchasing any plant. Learning the hard way is not fun.

Mine has brown leaves from down pours of rain. What are you suppose to do? Not in a pot.