Hopefully, you're well on your way to digging out from all the snow! Anyway, aqauatic plants take weeks to get used to new tank water conditions. What you can do is give the plants time. The plants will die back and slowly recover.
In the mean time, you need to maintain good levels of phosphate, nitrate and sulfate by doing large, weekly water changes. As a supplement, I dose a good liquid fertilizer a couple of times a week when I top off my tanks. API, Nutrafin and Tetra all have good products you can get at the pet store.
You don't have to use liquids, there are fertilizers in granules, dry, tablets, etc. that will work too. You should take the time to research the lighting requirements of your plants too, just to make sure you're providing enough. Ideally, you want lighting in the 6500K range.
Just a couple of thoughts.
"Fear not my child, just change the tank water."