I am not too far from you...we have two ft plants in unheated greenhouse that shriveled too.
On your coots soil mix did they tell you what the ph level is?
are your plants doing better today? weather is warming up quick
which batch of coots mix are you asking about, our old stuff from last year, or the new batch? either way i haven't gotten them tested yet.
I really like the coots mix. The lava rock makes it hard so you can walk on it without leaving tracks. well at least i can, maybe not somebody who is over 200lb or so. anyway that makes it easier to work on plants in 8ft diameter pots cuz i can just stand in the pot