We just don't have nearly enough information to give you an answer. Your links (when properly deciphered from the raw code you posted) show chickens, which may be pets but don't need fertilizer (they produce it).

Hi fugal,

Too much nitrogen would be my guess. Half strength 20-20-20 is the same as full strength 10-10-10. Way too much fertilizer! Actually, for seedlings that small you may not need any fertilizer at all (depending on the growing medium). If the growing medium has absolutely no form of fertilizer, I usually do add just a very small amount of water soluble fertilizer. Seedlings that small should have no more than about 100 or 150 ppm (parts per million) nitrogen. Using 20-20-20, that means about one half teaspoon per gallon of water :-)
You probably should flush the growing medium by adding water until it runs out the bottom of the container. This would help remove any excess salts that have accumulated due to over fertilizing. Actually, at this point, IâÂÂd probably transplant the seedlings into their own small pots. You could use a growing medium that contains enough nutrients to feed the plants until theyâÂÂre planted outside (Scotts Miracle-Gro potting mix for example). That way, you wouldnâÂÂt have to worry with fertilizing at all.

Just my opinion of course,

Art

Thanks again Art! I'm sure you're spot on here......... Rookie mistake! I was prolly using 2x the correct amount! I'll try flushing some of the salts out in hopes of salvaging some of them..... :(

It sounds like Art may be correct with his GUESS (since you confirm that you over fertilized). However, I still don't think we really know, because I doubt you really have an accurate way of estimating how much fertilizer was actually applied. If you "feel" that you did over fertilize, then by all means see if you can flush a little through the growing medium. But, with the information we have so far, about all we know for sure is that you used some fertilizer and that have a picture of chickens.

I use 1/4 strength 10-10-10 on my petunias. You say watering isn't the issue, but when I see yellowing seedlings, my fist though is over watering.

Agree with mandolls - over-watering. No doubt you are over-fertilizing but you are also over-watering them. The varying turgidity in the leaves shows that to be the case.

Dave

Thanks mandolls & dig dirt for your input! In my own defense, I had just watered before taking the pic...... That said, I do struggle with ProMix retainging moisture (which is what it's supposed to do)...... I've taken to using a small fan for air circulation as well as helping dry the media....

The over fertilizing thing is a more glaring mistake...... Don't have any excuses to offer on that one other than ignorance... :)

Glad I could be of help, Cugal!