HELP...Heater Problems

[tomato clown]

I have 3 heaters and the oldest one is the only one working properly. I had bought 2 TopFin heaters from the pet store, they are 75Watts each, and don't get 2 of my tanks above 76degrees. this is a sudden occurance. They had been working great.
Do I need higher wattage, or a different brand heaters?
Dan

 

[tomato clown]

sorry to burden everyone with this post, after I posted I did some looking arround and found my heaters were not plugged in, apparently my daughter unpluged them last night.
Dan