Just bought some T8 LED bulbs to replace the fluorescent tubes in my shoplights from Menards. Supposedly these are direct replacements for the tubes I had in the light. According to the specs -" The most common applications for the GT-LITE 17-watt 48" T8 linear 5000K LED light bulb are direct replacements for 32 watt linear with instant start ballasts". When I replace the bulbs with the LEDs I bought they don't work unless one of the old fluorescent tubes is installed in the other half of the fixture. I tried this in a few of my other fixtures of the same type with the same result. Is this a symptom of a ballast incompatibility with the LED tubes?