Indoor plants died overnight, heat issue?

[Kalium]

I have been scratching my head over the past 3 months trying to figure this out - something is killing all of my poppy sprouts in what seems like one fell swoop, over and over again. The leaves turn dark/purple and the plant wilts and dies, once it starts the plant is done for.
Other plants in the indoor garden are fine. It was quite hot yesterday but I have fans blowing on all the sprouts, maybe this is related? Yesterday these guys were green and full of life - one is still hanging on.
I have been trying different things like more fertilizer, less fertilizer, pest control, disease control and isolation. Nothing seems to be saving these poor guys! Im really leaning towards a temperature issue. I started one outside at the same time that is doing just fine..

 

[Marck]

Perhaps there is a type of damping off fungus for which this type of poppy is particularly susceptible.

It is unusual looking for a poppy seedling. What kind of poppy is it? Do you have a picture of a larger plant?

 

[Kalium]

I do not have a picture of a full grown one, but I have grown them to maturity before in the same room. However, the issue started to appear on them on one generation while they were halfway thru growing.
What seems to be going on now , simply stated, is that they grow fine for about 3 weeks from seed then die in the same fashion. They are "gigantum" Papaver somniferum from California
Is there anything you recommend to mitigate or check for this fungus? I have tried the copper fungicide power (bonide) and I use mosquito bits in soil to manage fungus gnats (which also may be to blame)

 

[Mrsclem]

What type of planting mix are you using?

 

[Kalium]

I do not have a picture of a full grown one, but I have grown them to maturity before in the same room. However, the issue started to appear on them on one generation while they were halfway thru growing. They grow fine for about 3 weeks then die. They are "gigantum" Papaver somniferum from California
Is there anything you recommend to mitigate or check for this fungus? I have tried the copper fungicide power (bonide) and I use mosquito bits in soil to manage fungus gnats (which also may be to blame)

This issue also causes the flower buds to turn purple (if they make it to that stage) and not bloom/grow, just die and start a new shoot

 

[Kalium]

What type of planting mix are you using?

Roots Organic Formula 707

 

[Marck]

Kalium, do you think your seedlings look different than usual?
In the first shot before the seedling is withered, it seems to be darker and shinier than what I would expect with Breadseed Poppy (Papaver somniferum) seedlings. My P. somniferum seedlings are usually colored pale blue green with a matte surface.

 

[Kalium]

Kalium, do you think your seedlings look different than usual?
In the first shot before the seedling is withered, it seems to be darker and shinier than what I would expect with Breadseed Poppy (Papaver somniferum) seedlings. My P. somniferum seedlings are usually colored pale blue green with a matte surface.

I think they have been starting the same as usual, similarly as to what you described with the blue/green and matte. I attached two more pictures, one of a remaining healthy seeding that is starting to turn black and one of a recent sprout that was late to the party (next to one that perished overnight last night.) The healthy one and dead ones were all planted using the same soil at the same time.
I also wrapped some of the pots with doublesided tape (as a test) to prevent anything from crawling in, so whatever it is, is flying in the plant or already in the plant.

 

[Kalium]

After these died, I was determined to figure out what was causing it. Once again the seedling grew for 3 weeks just fine and I started noticing the darkness on the plant and I decided to check in the bottom of the pot with a digital microscope. There are a unbelievable amount of bugs in the soil.. disgusting!
Can anyone ID the brownish bug that looks like a termite? It did not appear to have "pinchers" but it has a similar body shape to a termite. I would say it was about 0.5-0.75mm length, 6 legs, whiteish brown color. The whiteish bug on leaf appears to be a springtail. Looks like there may be a soil mite in the soil shots?

 

[Marck]

The first insect looks like the immature stage of some type of tiny hemimetabolic insect, in other words a nymph. I'm not seeing antennae, which is unusual, but the may be very short, hidden, or missing.

The Springtails (Collembola) are harmless in themselves, though a very high population may be symptomatic of excessive moisture and rot.