If its cold, don't water. It'll hurt the roots.
The snow melt will be water enough. Wait to fertilize for it to warm up.

If your root temps are in temps of lower that 50 degrees, your plant will not take up nutrients anyway.
You can either waste the fertilizer and hope for a warm up so then it's there for the taking, or hold off as Rosey suggested.

Do you have a thermometer than can show you the temps of your soil and what the root zone is at?

I persoanlly would acidify your soil even now so that when your root zone does warm up, the nutrients that are still held up in your soil will be readily available and revert your leaves back to green.

They are in-ground, correct?

Mike

They are in the ground. The snow didn't stick and the soil was barely damp so I watered them since the temp bounced and is in the high 40s today. I bought azalea and Camilla fertilizer. But my dumb butt put the granules in my watering can and watered the plants. I quickly realized that wasn't going to work and dumped the fertilizer around the plants and watered them hoping to wash the fertilizer off before it burned my gardenias!

Wreckitriz,
Test the PH level in your soil before you worry about wether or not the Ph is acidic enough or not.
Go to any home center for a test.
Gardenias are evergreens and don't photosyntheise if the temps are below 40 degrees.
Unless you go WEEKS without water, rain or snow, don't worry about them.
Yellow leaves are fine. Don't be alarmed at yellow.
Brown leaves from the bottom of the bush up is bad.
Just let it rest in it's mulch til the middle of April, it will be fine.
They are hardier than you think.
Like a Rhododendrum. Think a rhododendrum bush.

I did a soil test before I bought fertilizer. It's extremely alkaline (dark green on the ph scale of test). It also tested low for potash nitrogen and phosphorus.

Wreckitriz,
I have some bad news. If your soil is very alkaline, and you want a beautiful growing flowering gardenia, if I were you, I would transfer it to a pot of potting soil as soon as the weather breaks and bury the pot in the soil if the water drains away fast enough when it's watered.
I have found that clay soil sometimes doesn't drain fast enough for plants that need excellent drainage, I lost a plumeria in a pot due to that.
It is SOOOO difficult to change soil from alkaline to acidic when it's planted in the ground.
It can be done, but if your soil is that alkaline, I would go the pot route, you will be much happier with your bush.
Gardenias can happily live in pots outside, you will just have to really protect it in the winter. Burlap will work too.
I use Foliage Pro on my potted plants, I bought it online a couple years ago. It is the best potted plant food, IMHO, because it supplements all the minerals neccesary for a potted plant so it won't lack anything at all. You will have perfect soil for it.
It is very concentrated also, so it lasts a long time.
Super thrive is good too, but I love Foliage Pro.
Good Luck with your gardenia, if you are really against a pot altogether, you could always dig it up when it gets warmer and dig out alot of the soil where it will be and replace all of the soil (ALOT of work), HD sells soil for rhododendrums and camellias GARDEN soil, and I would use at least one giant bag of it and mound it up for the gardenia for drainage.
Then you should be alright, til it settles......then more work.....and it goes on and on....LOL!
But we all love them and they are worth it!