Looking at the plants in the first picture I would say you've been overfeeding. But the second one just looks thirsty. If you say the pot feel heavy, then you might have a root problem. Smell the bottom of your pots. Does it smell sour? If so, you need to let the soil dry out so the rotting roots die off and shrivel up, then water with water and some beneficial bacterial/mycorrhiza mixture for organic soil. These little workers will sort your soil issues out.
Picture three...I would say is ok as she is full on flowering. Sometimes the plant can't keep up with the needed nutrients and this shows in the lighter coloring in the tips of the plant.
Pictures 4&5...If you sowed the seed directly into that pot and you water the pot completely, then you have watered to much. I always use the span of the leaves as a guide where to water. A small seedling doesn't need a lot of water and it's almost always better to let the roots dig deeper for water. You shall have to wait until the pot dries up and meanwhile use the finger test. Poke your index finger into the soil, somewhere in between the seedling and the side of the pot. your finger has three parts in it, we're starting from the knuckle and go down to where the nail is, ok
If the first part of the finger feels cold and/or wet, you've watered way to much for this stage and you need to wait until the water has evaporated*.
If the second part of your finger feels cold and/or wet...This is where your pot should be at the moment. This will attract them roots to go deeper into the soil in search for water.
If the tip of your finger feels cold and/or wet, it's time to water again.
Now, look from the top onto your plant and using the length of the leaves as a guide to how wide a circle around your seedling you should water. Water no more then 200ml into the pot as slowly as you can, without disturbing the soil. I use a piece of airhose with a stiff piece of hose at the end as a watering wand. It's normal for your seedlings to take two to three days to drink all of that...
Now, I do suggest you water with the bennies (like Bactrex/Mycotrex or anything you can get your hands on,
LINK) added to the water as these will help you resolve any issue with the roots you might have.
I would also stop adding nutrients to the soil and only give water with some magnesium sulfate (epsom salt) added to it. One teaspoon per gallon/5L of water will do. You can also spray that on the leaves, especially on the plants in picture 2&3.
If the pots are to heavy because of overwatering you should let it/them dry out. Adding a heatmat underneath the pots will help you do that faster and it'll help the bennies to get a better foothold in your soil. Don't let the temperature of the soil go above 28°C/82.4°F as this will kill off your mycorrhiza, but keeping it at 26-27°C/79-80°F is A-ok. Feed your bennies with some carbohydrates in the form of molasses. Use the cheapest you can find and it will have all the micro's you'll ever need. Don't overdo it. Add 5ml/L or 20ml/gallon water together with the bennies in the same water. Make enough for one go as the mycorrhiza spores can only be in the water for 6 hours or so. If you are only using beneficial bacteria then you can let that stand for up to two days after which you will need to add more molasses as all the carbs will be gone, but the amount of bennies in the mix will have exploded
Hope this rant helps a bit in understanding how to take care of your soil, when you master that the beneficials inside the soil will take care of the rest.
