Seedling diagnoses

I have tried those "biodegradable, plant directly" cups before and found two main/big problems with them. 1 - it takes forever for the roots to grow through the cardboard once you do plant them, and 2 - keeping the soil in the cups moist. They cardboard acts lick a wick and sucks all the moisture out of the soil. I found that as soon as the cardboard was dry, the soil was over dry and the only way to know if the soil was still moist, was if the cardboard was also moist. So, going on your info, warm air blowing, creating even more evaporation, heater pad and giving your babies cal/mag are all combining to make them unhappy in my opinion. Also, those cups are pretty small in volume, so the roots will be hitting the bottom and possibly burning from a combination of dry soil and the heater pad. Another thing, with so much perlite, which is inert/has no nutritional value and is really only for heavy soil with poor drainage, means that what little actual soil there is, will run out of nutrients pretty quickly. This is why the cheaper soil mixes have so much perlite, they want you to spend lots of money on high profit fertilizers! Good quality, well drained healthy soil only needs 3-5% perlite at most and probably none really. So, what to do? In my opinion, first give your babies a really good drink with plain water, until you can feel the cardboard is also wet/moist. Remove the heat pad to stop the cups from drying out so fast. Ensure there is no warm air blowing directly on your plants or their cups, this will only burn the leaves and rapid dry your cups. Your seedlings do not need any nutrients at this size/age, they are still small and delicate. If you are leaving watering until they are weightless, this is waaaay too dry, causing the droopy leaves. You want the soil moist, but not wet and some weight to the cups. I would also be considering transplanting the seedlings into bigger pots with fresh soil, sooner rather than later. I found that by carefully making some slits in the sides and bottom of the cardboard cups prior to transplanting, allowed the roots to "escape" from the cups much more easily and quickly. (I am a mad scientist and conduct all kinds of research/experiments. Too much time on my hands, being stuck at home with a disability I suppose. Besides, TV drives me nuts!) Also, is there nowhere else besides the garage that you could put your set-up? You seem to be having temp problems already and this could become an issue for your entire grow cycle. Much better if you could have it in the main house. If not, a standing column heater (oil filled) works well as a radiant heater without having hot air blowing on the plants, as hot air is going to cause all sorts of grief, as you have found out. Perhaps next time, start your babies in 3 or 4 inch plastic pots, they dry out much slower and make transplanting much easier as the soil/roots/plant just slide out, meaning the roots don't have to battle a cardboard membrane for freedom and accelerated growth. Deep pots work best - 4 inches wide by 5 inches deep are my favourites, as it allows enough depth for good root growth and enough volume to provide enough soil nutrition until they are big enough for transplanting, without the need to feed them before transplanting, assuming a decent soil mix. Good luck and happy growing, you are embarking on a voyage of discovery and learning, also a hobby for life! Feel free to message me if you have any questions. Hope this helps,..... Organoman.