A few questions. Are these onions that you are growing indoors under lights or are they onions that you purchased and planted out already? If growing under lights how long has it been since you started them? On indoor starts it is normal for the seed leaf to be rather spindly and white at the tip. Eventually after 5 or 6 weeks the seed leaf will completely yellow and whither away but this is after the plant has grown a couple new leaves.

Jack, the very tips of I think the first true leaves are a little yellow. It is more visible today in the sun. I think it could just be related to the trimming damage but could also need fertilizer (it shouldn't as the mix is enriched) or be overwatering. Does that ever happen to you?

Yes, after trimming the top 1/2" or so of some leaves will sometimes turn white. Doesn't seem to bother them. You might need to fertilize. Sometimes after watering several times there is not much of the nutrients left in the potting mix.

Thanks. I will give some diluted MG next time I water, but I haven't had much runoff from the tubs. I try not to water to the point of runoff, but I am learning when plants get larger the roots fill up the space and water doesn't penetrate as well and waiting for runoff is a good idea, or do bottom watering. Luckily with the clear tubs I can see the water doing its thing.

These are outdoors and it looks like the original leaves from the plants are the ones changing colors not the new growth. I think it's been a couple weeks since I fertilized. Time to feed them again?

Please provide more info. Are they transplants? How long ago? How much are you watering? What did you fertilize with? How is you soil? Drains well? Nutrient rich? Post a picture?

Transplants, planted about 40 days ago. I've been watering once the soil starts to dry, but not flooding the area just making sure it stays semi moist. the first two times I fertilized I used a higher nitrogen miracle gro(not sure of the ratio but I can get it). I'd say the soil drains okay it's a nice mix of topsoil, sand, compost and peat. I can post a picture when the sun comes back up.

Yes it is probably time for more. Your mix is probably low fertility, and MG is quickly washed away. I would add some organic fertilizer like Garden Tone and more compost. Espoma products have beneficial colony forming bacteria which will help break down the compost, and wean off the MG. Is it a raised bed? JMO. Maybe Lonejack will have different/better advice.

Where are you located? Are these short day type onions or intermediate day?

I fertilize onions with a 10-20-10 ratio mix a couple weeks prior to planting and then about every 3 weeks I use urea (46-0-0) at about 1 oz. by weight per gallon of water. I wait about 1/2 hour for the urea to dissolve after adding it to the watering can. I stop fertilizing and watering by early June when they begin to bulb up here. This is for long day or intermediate day onions in my locale so if you are growing short day onions further south you will have a different schedule.

If you go to the Dixondale farm website there are very good instructions for growing onions.