First time I have seen this happen. I recently replaced my floodlight "try" but didn't like them for several reasons and put my old T5 fluval fixtures on the tank. They have been on a week or so and really liking the tank again. I had a single fixture unused and decided I'd like another "punch" to the tank and put it on this evening with a brand new 4100k T5 from Home Depot I picked up today. It added the touch I wanted.
Since adding that light this evening I noticed my plants were pearling maybe 4 hours later. Would adding this extra light be the reason for this? I am interested in knowing if this could be the reason. All other things are the same...non co2 and have not done a water change. The other tubes are 2x10000k and 2x 6400k. Thanks for any input.