Normally, low light causes leaves to darken but too low will mess with photosynthesis (think green and white asparagus). To me, your plants don't look like cold damage but an imbalance of light to nutrients.

Your N dose is okay. Check your fertilizer for iron and magnesium. Their lack often causes chlorosis.

I've looked up nutrient deficiencies in phals and the leaves look very similar to mine! I've placed my needy children right in the bay window to relieve more light, and I've given them a heat mat and a little plastic dome. Hopefully these conditions will ease thier stress a little. The fertilizer i ues does contain trace elements like iron, copper and magnesium.

Good luck!

Make sure the move isn't too sudden/drastic a change in light. The dome should protect it some but how much?

Consider adding supplements. I'm not familiar with what forms can be used by plants (I use a cal/mag formula from the hydroponics store). If someone here doesn't pitch in, do some googling.

The plants were moved about 10ft closer to window, where they were before the gloomy winter weather started. The sun is much less intense now and the dome is slightly opaque.