struggling seedlings whats wrong?

[RayR]

Originally Posted by pecker88

I used dye drops, no electronic pH meter. After 3 drops per the instructions, it immediately turned red, indicating low pH. RO water is about 6.5.

That seems impossible that condensed water vapor could have as low a PH of 4.0. Your typical PH indicator dyes may give very erroneous readings in a low ion solution just like an electronic PH meter will. There are special indicator dyes that can give accurate results of a low ion solution but those aren't found in your typical PH test kits.