Scratching my head, You sure did encounter a lot of problems with this start of grow, Im going to be honest about a few things. Soil with nutrients is not a bad thing, even for seedlings, I have all kinds of nutrients in my soil, That's what the plants need to grow healthy. Another thing that Super Thrive is no good, I hear people using that stuff and it's just the worse stuff you could use for cannabis and esp. seedlings. The nutrients in the soil is good enough to grow a healthy seedling. Another thing That perlite is not needed in a seedling tray or those small pots you have. You gotta have a good mix of soil in there for them to grow healthy roots and perlite does not have anything in it. Just a waste of space honestly. When you transplant and want to use a mix of that then sure it's ok.