Nitrogen deficiency

Just a quick question. I planted a new garden and my transplanted kale and broccoli seem to have developed a nitrogen deficiency. I've treated it with fish emulsion and just want to know how I know the problem is resolved. Will the yellowed leaves turn green again or will I have to wait and watch that the new leaves stop going yellow? Thanks.

Both will happen.

If the existing lower leaves are really unhealthy, they won't green-up too much, but you should see some improvement.

But you should see a flush of new healthy growth. You don't want to over fertilize them, as brassicas tend to become aphid magnets when they grow too many young tender leaves for the bugs to munch on. (At least mine do).

Those first leaves that stick out sideways at the base of brassicas tend to be funky. They'll start to dry up as the plant matures.

Hi Brandon Most of you question was answered by Marco, I would just add:

Not sure of your location(s)? We are having a very cold spell here, In North East. Going to slow everything down.

For most fertilizers it takes about two weeks for a return. The liquid fish should do the job. Better to have too little then too much.
Keep off plant place around the outside edge let the plant go after the fertilizer is always a good idea. That said don't place it too far away.

Ten four to that verdict,thing I've learned is take fertilizer slow,it's easy to overcompensate.
You Also said "new garden?"

Want greenery in your scenery? Pee on it. 1 part urine to 10 parts water. Green up anything you want to produce lots of green leaves.

Without knowing your situation, it's difficult to make a suggestion. Questions that come to mind...
...is the soil pH suitable for broccoli?
...is the adequate soil drainage, or is it waterlogged?
...were the seedlings stressed prior to transplanting? Had their growth been interrupted by drying out, windburn, sudden chill?
...were the seedlings being fertilized while growing?

Normally I don't apply nitrogen when I transplant broccoli seedlings. I'm more apt to apply a bit of phosphorous until they become established. But then again, my garden beds get a light tilling of an inch of compost between crops.

Now I'm no soil expert, by far. And I don't have to deal with soil temps below 55° F. But I do recall from a college ag course that soil temperature has a bearing upon the availability for nitrogen uptake in field plants. The type of nitrogen source makes a difference in cold soils. Plus when it comes to organic home created nitrogen sources, such as compost, most of the nitrogen component needs to be processed via the soil microbes before it is in a form useable by the plants. Sadly I have no idea what this would mean to you, since it all depends upon your soil conditions and temperature.

Based upon my own personal experience, I see that my homemade fish emulsion, and urine, each work fairly quickly.....meaning seeing visible results in 2-4 weeks.