justaguy, Since you haven't fertilized them yet and they are growing in vermiculite, they are probably suffering from one or more nutrient deficiencies. I recommend watering them with one-quarter strength nutrient solution. Avoid any formula that contains urea as a source of nitrogen. Urea is fine in garden soil, where soil microorganisms break it down into usable nitrate or ammonium ions. In a sterile growing medium, urea doesn't break down or get used either, so it can build up to harmful levels. I use three different urea-free soluble nutrient products: Better-Gro Orchid Plus water soluble orchid food, 20-14-13 plus essential minor elements. Better-Gro Orchid Bloom Booster, 11-35-15 plus essential minor elements. Peters Specialties African Violet Plant Food, water soluble 12-36-14 with micronutrients Any of those three formulas should work fine, although the first one is probably more suitable at this stage of growth. I get the Better-Gro products at Lowe's and the Peters African Violet Plant Food at Home Depot, our local greenhouse/garden center, and various other places. None of those formulas contain calcium, so if you plan to grow those dahlia seedlings for any length of time in vermiculite, you should also supply some soluble calcium. I use calcium nitrate, which I purchase online at Everybody's Garden Center. I dilute the calcium nitrate separately to about ¼ to ½ teaspoon per gallon and combine the diluted calcium nitrate solution with a similarly diluted nutrient formula. By mixing pre-diluted solutions, you prevent the calcium from precipitating out your soluble phosphates as relatively insoluble calcium phosphate. MM

Hi Paulie, I too am growing seedlings at the moment, although mine are a little bit bigger than yours with a few more leaves. For comparison, I give mine about 6 hours of sunshine a day, some of which is filtered sun. I let mine dry out a bit before watering, but I do not let them dry out completely yet. Maybe yours are going too dry between watering especially if they are getting a lot of sun. Maybe they need to be a bit bigger first. It can be difficult to get right at this stage, & only you can judge what is best for your climate & conditions. Good luck with your seedlings. Rachel :)

From what you state that you are in the tropics and you have them under a roof structure, still getting sunlight. They should be receiving at minimum 8 hrs. of good sunlight every day or more. Extreme heat can be shaded such as you mention during the hottest part of the day. With you probably having good amount of humidity, this well be good. Roof structure will help the plants not getting too much rain if you are receiving much rain. I am thinking that the yellowing leaves are more from the soil. You may need to add some very porous material such as Lava rock, coconut husks (1/2" size). The clay pots can be an issue, especially if living in a very dry, hot area. If the you experience yellowing leaves and yet the plants caudex/stems are in relatively good condition. I would check for better porosity of soil and pests. Rick

Hung Dang, It sounds like they are responding to the change in light & temperature by going dormant. I don’t know what part of the world you‘re in but that would be a normal result this time of the year in the northern hemisphere as we begin the transition from Summer to Fall with shorter days & cooler temps. The one thing thats concerning is that your seedlings are so young. When I started mine from seed years ago, I was advised not to let the seedlings go dormant over the Winter & to continue watering. Months old seedlings don’t have the stores to help them survive the Winter like older plants do. I think I kept mine on bottom heat & near a South facing window, which kept them actively growing throughout the Winter. Once they start going dormant I’m not sure what you can do. Maybe the warmer indoor temps and brighter light will wake them up again. It sounds like you are trying to provide them with as much light as you can, so maybe they are just adjusting to the new setting and will begin to produce leaves in a couple of weeks. Nothing else to do but watch & see what they do. Like Socks says, be very careful with watering while dormant or in absence of leaves.