great work man!! this is how we learn. the guys imo were right on with over watered and overheated however canna can take a lot of heat.I have a different theory based on 37 years of growing experience.
begin lesson:
canna depends on several factors to thrive it is much like a fire in some ways. it basically depends on 4 things.
1, light whatever the source the more light the better and conversely with canna dark the is totally dark is important.
2, water as with all living things is important, city tap water works great for us and for canna, if your municipality uses higher levels of chlorine then I would recommend letting it sit out overnight before use on canna.
3, atmosphere yes air plants absorb a lot of carbon especially when they are growing vigorously, as well being moved by the air is an important component in growth and strength. fresh air blown around is best.
4, soil or other media, The great enigma what works best. I have personally grown in rock wool rock wool cubes coco canna pebbles in a waterfarm and aquaculture using a fish tank. After all the years of experimenting I have found that for ease of use, cost, and overall workability soil is best. organic live soil.
My personal thoughts on soil.
soil is the living thing that plants coexist with naturally to grow and thrive, however the plant is unable to absorb much of the nitrogen and other nutrients in the soil. The "soil herd" an army of microbes and other microorganisms must convert the nutrients into plant absorbable form. It is a symbiosis it works very very well.
My personal thoughts on adding chemical nutrients to soil
want to outright kill the soil herd? add some miracle grow or any synthetic compound to the soil. sounds terrible right? Well it is and isn't. plants cannot tell the difference between the chemically broken nutrients and natural ones so as far as the plant are concerned its all good however it has been my experience that chems in soil ruin the taste of bud.
What I use and would recommend
Fox farm ocean forrest thats it no mas no nada I make teas out of liquid bone and seabird guano and add in bat guano in flower. My soil has a bigger herd at the end than at the beginning.
here is a picture of my soil look at the difference between that and the soil you transplanted into.
A good rule of thumb is to get high quality soil and love it.