Jamie, 15...is that Celsius then? So approximately 60F, not particularly cold for the beginning of winter and certainly not for hydrangea. Length of daylight hours factors into the winter dormancy too, not just cold. Your hydrangea is a deciduous plant and should be expected to lose leaves in winter - in a mild climate at least some of them. Your plant will be happier/healthier outdoors than in your house, take it back outside.

If you think it is the waterlogged soil, can you transplant them someplace less wet?

Wow! Three times a day is excessive to the nth degree! I have to assume the person did not understand your question na dhe/she meant something else. In my similar weather, I do not water that often. To determine when to water, use the finger method daily in the morning, as follows: Insert a finger into the ground to a depth of 4" and give the plant 1 gallon of water when the soil feels dry or almost dry. Make a note on a wall calendar whenever you water. If the soil feels moist, skip watering. If the soil feels wet, determine why and take any appropriate course of action to correct the wet conditions. After 2-3 weeks, review the watering notes that you wrote on the calendar and determine, on average, how often you were watering (say, you watered every 2/3/4/5 days). Then set your sprinkler to water 1 gallon on that same day frequency (1.5 gallons if your soil is sandy). Water early in the mornings. Too much water for long periods of time can make the roots develop root rot: They will first be deprived of oxygen if clogged with water, Then after a while, the existing fungi in the soil will begin to rot the roots and the plant will wilt 24/7 no matter how much water you give it. To help alleviate the problem, temporarily remove any mulch that you have... say, for one or two days and put it back when the soil no longer feels muddy. After that, maintain 3-4" of mulch up to the drip line or several inches past the drip line. In most places, you can keep the mulch up to the drip line but, where temps frequently hit the 100s (for two months in a row here for example), even light breezes help the leaves loose moisture quite rapidly and slightly more mulch will help keep the soil cooler and moist longer. The yellowing of the leaves is being caused by the plants not being able to get enough oxygen. The roots are plain colgged with water and canot breathe well. So remove the mulch to make the soil dry out faster. Then return things back to normal in a day or two, when the soil feels moist, not muddy. Luis This post was edited by luis_pr on Wed, Jul 3, 13 at 23:35

Another thing to check out is hole under the plant draining off the water. Sometimes vole and moles make a opening hole without a mound near the base of my hydrangeas. The first sighn is the leaves suddenly droop even though the plants have had water.