interesting situation. i imagine it would be difficult to modify for the better. take that dehumidifier out if you feel it's better. try a heat sink made with buckets or drums filled with water. you know, for the dew; if it's that big an issue.
ventilation doesn't make sense to me anymore for the same reason as you. things don't quite work with the humidity so low. i'm seeing that 1"/day growth instead of sickly and spiny. odor hasn't been an issue so far, i hope the extra humidity will dampen it haha.. dampen
looks good thrasher. make sure you water with that reverse osmosis between fert. every other time or every third time those tops are starting to burn. this burn happened to me in a different way: it was a heat stress/ salt buildup combo from me using tap water.
the leaves may be too warm for the what i assume is low soil temp or, the soil is not drying fast enough in those cups. stick a thermometer in the soil and see what is up
you may want to flush these or transplant them in new soil. the fert amount you're describing is for a foot 30cm plant. not sure what aqua safe is and ph is tricky you may have a concentration of one nute in there anyways. distilled water will work and transplanting will save your dirt for...
Soil
I've been really upset with ventilation equipment lately and in re-arranging things i remembered a post where one guy was advocating that co2 isn't necessary in a closed system, not just sealed, closed. He had a co2 system ready but found it was unnecessary going by the readings on his co2...
what i see here is coils in the 250/w fighting one another before reaching plant matter. you're right a 400/w would do the same but they are a drag if you know what i mean. true the extra heat may make it a poor alternative. do what you're happy with.
4 T-5 Tubes in a grow tent is a great setup. They stay warm and you really don't have to do much venting. HID lamps become a burden in a grow tent because of all the venting necessary. If you're worried about yield finish a grow and see what you get then do it again with the same genes and...