Two of the seedlings were showing some really marked chlorosis. A little odd, because all 4 buckets should be the same mix, but... I checked the EC of all the buckets and they were consistent. pH was a smidge high on those two, so I dropped it from about 5.8 to closer to 5.4/5.5. After a couple of days, I decided to just remix those two buckets. I didn't want to spend a lot of time trying to fiddle with a nutrient deficiency with autos. After a couple of days the meristem areas were coming in green again, so hopefully it's fixed! The other two plants looked fine.
Edit: Immediately after writing this entry, I was like "Oooh, it's nute burn." so I dumped 1/2 of the reservoirs and replaced with filtered water to get the ppm down. pHed it to 5.5 again, and we'll see!