First Grow, Weird Symptoms

So SWIM started his first grow 3 weeks ago. Up until this week, nothing was going wrong. SWIM was watering them with DynaGro foliage pro as of last week but they seem to be getting sicker. SWIM looked at so many pictures but couldn't diagnose it as there were too many similarities between different problems. Here is the basic grow information and some details about each plant:

Indoor grow
Watering every 2-3 days when top soil is dry
Started in potting soil, been fertilizing since last week
Vegetative, 3 weeks in

Plant 1 is the first image(p1). This plant has had the least amount of problems but is now showing a tiny brown spot on the tip of the bottom leaf(bottom left corner).

Plant 2 is images 2, 3, and 4. The stem is turning red towards the top(p2_1) and like the others the bottom pair of single leaves are browning and drying(p2_3). Also, some of the bigger leaves are turning light green and one has a brown spot on it(p2_2).

Plant 3 is the last image(p3). The tips of some of the main leaves are browning and the pair of single leaves died and fell off this morning.

One last thing SWIM forgot to mention. Plant 3 is experiencing very weird leaf symptoms. Some of the leaves only have 4 blades, some have an odd number but are curling outwards in weird patterns, and some are completely fine.

From what I see, it looks to me like a nutrient burn, could either be from the nutrients its given (dosage amount or type) or from the soil. Nutrients in the soil are released each time the plant is watered so it could either be too strong of a nutrient soil or the type of nutes being fed.

The burnt tips and edges indicate nute burn.
The nutrients in the soil plus the fertilizer you're giving it is too much.
I had this same problem on my first grow. When are the nutes in the soil used up?
I'd say wait at least 4 weeks before adding nutes into potting soil and then when you do, add in 1/4 strength of recommended and see how they do. If they respond well, no discoloration or burning, you're good to go.
Please note that the damaged leaves won't be repaired but watch the new growth. If it's green and happy then you're good.

Looks more like overwatering leaching P, K, and Mg.

Olive Drab Green said:

Looks more like overwatering leaching P, K, and Mg.

Click to expand...

Good point.
OP, do you know the watering method of waiting until the pot is light before watering?
Like light as in dry. If you fill a pot with just your soil, not watered. That light. And if you think that its light enough, wait another day and then water. And when you water saturate. Don't let them sit in it. They don't like to have wet feet.