Little bit of nute burn

Currently have 7 Shiva plants going. They are 9 days from first sprouting. Grown in rockwool/hydroton mix in ebb&flow. I use AN nutes 3 part (full line with additives). I feed 3xdaily for 15 mins. I just started them yesterday at 1/8 strength nutes (ppm 284). The plants look awesome, only 3 inches tall, but 4th set of leaves on most of them. They are lime green and lovely. They have run three feed cycles and my ppm have been 284 when fresh nutes mixed, 307 after first feed, 287 after second feed 285 after third feed. SO..they are eating well and balanced. All seems fine...BUT...I have one little lady that has nute burn. This is only my 6th grow, but I have never had nute burn before. I run my ppm's low. The other 6 plants have no burn and look great, but this one has a burnt cotyledon and a little edge singeing on leaf set 1.
I flushed the pot with 1 gallon of RO water, pH 5.7 and elevated it off the table so it will not eat with the other plants until I lower it.
I guess my question is how long should I wait until I feed this baby again. The soup is pretty weak, and the other babes aren't burning, so why this little sugar?
Anyway....advice, insight, input, insults.....just hope to hear something. LOL.
Peace all!

Whats the genetics on shiva? My guess is that you've got a strong sativa pheno out of one of those seeds, and they don't take nutes as well. My Sweet Nightmare babes did the same thing last year. If you don't mind hand watering a lower dose for a week you could do that...or lower the res ppm...the others shouldn't mind it. You could always foliar feed any ones that look deficient.

For those who care.....I did not nute burn a plant at 300 ppm. My wife just admitted that when she went to add pH down (per my request) to the res some dripped on that little girl.....burning her. I really though that 300ppm was way low to burn any plant...especially when the other 6 didn't burn. So..the mystery is solved. now...what about the seed in my widow???