First Grow - RQS Watermelon/RQS Critical

After two full weeks of water cup and covered germination station, transplanted all seedlings into 1 qt pots with Fox Farms Happy Frog soil. 13/15 plants seem to be taking well to the transplant. Two of the watermelons and one of the critical are struggling and may end of being tossed. Was struggling to keep temps up with the LED lights off so a ceramic heater set at 70 deg F was added. I also added 2 DIY C02 generators using 2 cups of sugar and 2 tsp of active dry yeast for each generator to try and boost the C02 levels is a bit.