leaf falling n yellow

That's Nitrogen deficiency (primarily, at least). The substrate's pH should be checked before attempting to fix the condition. Low pH locks out N.

The downward curling may be a separate issue. Since it seems worse toward the bottom, it could be from a overwatering.

 

The watering issue isn't serious and the plant should perk up after it's fixed. The lack of N inhibits food production by the fan leaves and is going to affect the final yield, but not necessarily by alot.

Watering cycles should go from damp all the way through all of the soil, to nearly dry. Don't water until the pot feels noticeably lighter and the top few inches of soil are completely bone dry. Then, water until all of the soil in the pot is damp. You can carefully pull the plant from its pot afterward to see how thoroughly you watered. Only pull plants in dim lighting to protect the root system. In extremely hot and dry conditions, plants in appropriately sized containers still go at very least 3 days between waterings. In ideal growing conditions, your plant should go at least 5 days between waterings.

 

I've done this before by adding too much nutrients. I had nutrient lock out. Just another possibility for you...

 

Be sure to check the soil pH, as Pheno restated. If the pH is low enough, no amount of N will help because it's locked out.

Some of the best sources of Nitrogen include Fish Emulsion/Hydrolyzed Fish, high-N Bat & Seabird Guanos, Worm Castings and Blood Meal. The Fish ferts are easiest to use, as they're already liquids, and are also the least expensive. Everything else listed here needs to either be mixed into the soil or made into teas for manual fertilizations. Fish-based liquids unfortunately don't have as long of a shelf life as any of the others. The Guanos are generally the best of the above fertilizers and are also the most expensive. They usually contain every micronutrient pot plants need and frequently in nearly ideal proportions. Worm Castings have relatively low levels of Nitrogen but contain many micros like Magnesium, but little to no Iron. They are best used mixed into the soil because unlike the others, they have an excellent texture for substrates and aerate the soil. Because a large portion of the soil can be castings (often 20-25%) without burning the plants, the low N concentration is made up for by quantity. Blood Meal, however, is very high in Iron, Calcium and other nutrients. It's inexpensive and commonly available.

 

Once you know what the pH is, you can either flush or neutralize the pH with an opposite pH liquid. Flushing is better for major pH adjustments. Neutralizing is better for small adjustments.

 

The second pic is showing alot of Phosphorus deficiency. While that could be the cause of the dead leaves, you should pull the plant and check the roots for binding. Root binding causes both dying leaves from the bottom up, as well as drooping just after watering.

 

Flush them, that's the best advice I can give. Fill a large cooler or some other container (you'll want at least twice the volume as your pot) with neutral water, add a 1/2 tsp of baking soda per gallon. Remove the plant from it's pot and submerge it in the water. Put an aquarium bubble wand in there for circulation, or just stir it gently every few mins. Allow the root mass to soak (is a dimly lit area) for about an hour. Now repot the plant. Don't water it for at least a week. It should show signs of improvement.

 

Also, what kind soil and nutrients are you using?

 

I'm sorry to disagree but flushing deficient or rootbound plants will very definately aggrevate either condition. If they are bound and it's bad enough, flushing can kill them.

You can pull a plant from its container at nearly any stage. The only time when doing so is a bad idea is when the roots haven't fully grown into the soil. For plants that size, you don't need to worry about that.

First, loosen the soil from the pot by squeezing the container's sides. With smaller plants, it helps to tilt them to the side or even upside-down when pulling. With yours, it'll be safer to leave them upright. Grab the base of the trunk, lift and separate. Do this in dim lighting and gently put them back as soon as you've checked the bottom of the root ball. An assistant would be helpful so the person holding the plant doesn't have to be the one checking the roots underneath. If no one is available, it'd be easier to check the bottom when pulling the plant from a seated position. If the roots are swirling in circles around the bottom & in any crevices, they are at least beginning to bind.

With smaller plants, you can often place your palm on the soil's surface with your fingers spread out and the trunk between two fingers. The plant is carefully turned upside-down, the container simply pulled off and then gently put back on.

 

I believe that the deficiency is caused by a low pH. Called me crazy but it sounds like Renizo was watering too often, and in insufficient amounts. Which would lead me to believe that fertilizer salts have probably built up in the soil, because of inadequate runoff.

 

Strictly speaking, a couple of the longest roots can start to swirl without the whole system being bound, especially if they grow into a small crevice at the bottom of the pot where they can't grow laterally. In that case, it would be obvious that it's only a few of the longest ones and there would still be unrooted soil between them. Serious binding would have the entire bottom covered in roots with many of them swirling.

 

Rather than grabbing one and posting it here, let me suggest typing "rootbound" into Google images. Lots of good examples come up.