They do drop their buds if it does get too hot.

Stop the fertilizer and see if that helps. Too much fertilizer seems to inhibit bloom on my hibiscus as well. If it resumes blooming, just give an occasional shot of half strength food. Too much and you'll get lush growth, but few flowers.

Too much fertilizer is bad. Well its not really bad, but as mentioned above it maked it go into active growth mode and will actually abort flowers. When you fertilize it, which should be about once a month, make sure that its high in phosphorus which is the middle number out of the three bottom numbers you see on the bottle. A high first number will increase growth.

Also the heat can do it sometimes too especially if its a dry or especially sunny heat which is why heat isnt as much of a problem on the coast. I would just keep it well watered. They need water just about every day during the summer, but can go a day or so without, but dry up fast even in large pots.

Good luck